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LABORATORY EXERCISES 

FOR A 

BRIEF COURSE IN CHEMISTRY 


BY 

LYMAN C. NEWELL 

n 

PROFESSOR OF CHEMISTRY, BOSTON UNIVERSITY, BOSTON, MASS. 


AUTHOR OF 

“experimental chemistry,” “descriptive chemistry,” 
“general chemistry,” “practical chemistry” 




lit 


:> 


o 


D. C. HEATH AND COMPANY 

BOSTON NEW YORK CHICAGO 

ATLANTA SAN FRANCISCO DALLAS 

LONDON 




Copyright, 1927, 

By LYMAN C. NEWELL. 

2 F 7 


© Cl A999102 


printed in tj.s.a. 

JUL-2277 


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PREFACE 




This book contains laboratory exercises for a brief course 
in chemistry. The exercises are divided into two groups — 
minimum and supplementary. Each group is numbered 
separately. 

The minimum group consists mainly of the exercises sug¬ 
gested by a Committee of the American Chemical Society as 
a minimum laboratory requirement for a year of chemistry. 
Besides the suggested exercises, this group contains a few 
others, some for the pupil and some for the teacher. On page 
xi there is an annotated list (List A) of the exercises for a 
minimum course. 

The supplementary group contains these kinds of exer¬ 
cises : — 

(1) Exercises which may be substituted for corresponding 
ones in the minimum group. 

(2) Exercises desirable for a course longer than the mini¬ 
mum. 

(3) Exercises needed for pupils who can do extra labora¬ 
tory work. 

(4) Exercises suitable for demonstration by the teacher. 

On page xi there is an annotated list (List B) of the sup¬ 
plementary exercises. 

This book has three new and distinctive features. 

(1) Questions are omitted from the laboratory exercises. 

(2) Instead of questions, precise directions for observing 
essential results are inserted in the proper places. 

(3) At the close of each laboratory exercise there are 
specific instructions for writing the notes. 

This plan of directed observing and specific recording will 
produce more satisfactory laboratory w’ork and more accu- 


m 



IV 


PREFACE 


rate laboratory records. Moreover, this plan will lighten 
the teacher’s task of examining laboratory note books a 
desirable and welcome relief. 

The apparatus needed for most of the exercises is simple. 
Many pieces are interchangeable and are used frequently. 
In some exercises a choice of apparatus is offered. 

The introductory pages (1-2) contain some general direc¬ 
tions needed at the outset by the pupil. 

The Appendix contains detailed directions for general 
laboratory processes, a brief treatment of the metric system 
of weights and measures, and full lists of the necessary 
apparatus, chemicals, and other supplies. 

Lyman C. Newell 

Boston, Mass., 

April, 1927. 


CONTENTS 


Numbers indicate exercises. Supplementary exercises are marked S. 
Teacher’s exercises are marked T. Essential exercises are marked ★. 
See Suggestions for Teachers on page xi. 

PAGE 

Suggestions for Teachers .xi 

General Directions for the Pupil . ... 1 

Apparatus — Laboratory notebook — Doing laboratory 
exercises. 

Properties — Chemical Change — Mixture 

— Compound.3 

1 — Properties and Chemical Change.3 

★ 2 — Mixture and Compound ...... 4 

SI — Decomposition of Mercuric Oxide .... 6 

Oxygen . 7 

★ 3 — Preparation and Properties of Oxygen .... 7 

4 — Heating a Known Weight of a Metal in Air ... 9 

S 2 — Examples of Chemical Change in Exercise 3 . .11 

S3 — Preparation of Oxygen (Short Method) . . .12 

S 4 — Preparation of Copper Oxide.13 

S 5 — Slow and Rapid Oxidation — T.14 

Carbon.15 

★ 5 — Properties of Charcoal . . . . . . .15 

★ 6 — Reduction of Copper Oxide by Carbon . . .16 

★ 7 — Preparation and Properties of Carbon Dioxide . . 17 

8 — Preparation and Properties of Carbon Monoxide — T . 18 

S 6 — Combustion and Carbon Dioxide .... 20 

S 7 — A Fire Extinguisher and Carbon Dioxide — T . . . 21 

v 










VI 


CONTENTS 


PAGE 

Hydrogen.22 

★ 9 — Preparation and Properties of Hydrogen ... 22 

★ 10 — Reduction of Copper Oxide by Illuminating Gas . . 24 

★ 11 — Reaction between Sodium and Water — T . . . 25 

S 8 — Preparation of Hydrogen (Short Method) ... 27 

S 9 — Reaction between Zinc and Sulfuric Acid — T . 28 

S 10 — Reduction of Copper Oxide by Hydrogen — T . 29 

Water.30 

12 — Purifying Water by Distillation.30 

★ 13 — Suspension and Solution of Solids in Water ... 31 

★ 14 — Effect of Heat on the Solubility of Solids ... 32 

★ 15 — Formation of Crystals ....... 33 

★ 16 — Effect of Shape on the Solubility of a Solid — T . . 33 

★ 17 — Testing Crystals for Water of Hydration ... 33 

★ 18 — Per Cent of Water of Hydration.34 

19 — Electrolysis of Water (Acid Solution) — T . . . 35 

S 11 — Preparation and Properties of Distilled Water — T . 37 

S 12 — Purification of Water — T.39 

S 13 — Anhydrous Compounds.39 

S 14 — Efflorescence — T.40 

S 15 — Efflorescence and Deliquescence — T . . . .40 

S 16 — Supersaturated Solution — T.41 

S 17 — Qualitative Composition of Water — T . . .42 

Equivalent Weights — Formula.42 

20 — Equivalent Weight of Zinc.42 

★ 21 — Equivalent Weight of Magnesium .... 45 

22 — Formation of the Compound Copper Sulfide . . 46 

S 18 — Equivalent Weight of Aluminum .... 48 

Chlorine and Hydrochloric Acid .... 48 

★ 23 — Preparation and Properties of Chlorine ... 48 

★ 24 — Hydrogen Chloride and Hydrochloric Acid ... 50 

★ 25 — Tests for Hydrochloric Acid and Chlorides ... 52 

★ 26 — Insoluble Chlorides.53 

S 19 — Preparation and Properties of Chlorine — T . .53 

S 20 — Chlorine Water — T.54 











CONTENTS 


Vll 


PAGE 

S 21 — Bleaching with Bleaching Powder — T . . .55 

S 22 — Hydrogen Chloride.55 

S 23 — Aqua Regia — T.56 

S 24 — Types of Chemical Change — T .56 

Air — Nitrogen.57 

27 — Per Cent of Oxygen in Air — T.57 


S 25 — Air and Combustion.59 

S 26 — Water Vapor and Carbon Dioxide in Air ... 59 

S 27 — Preparation and Properties of Nitrogen — T . .60 

Acids, Bases, and Salts.61 

★ 28 — Behavior of Oxides with Water.61 

29 — Neutralization.62 

30 — Neutralization by Titration — T . . . .63 

31 — Preparation of Salts.66 


S 28 — General Properties of Acids.67 

S 29 — General Properties of Bases.68 

S 30 — Two Properties of Many Salts.68 

Ionization and Ions .69 

32 — Electrolytes and Non-Electrolytes — T . . .69 

33 — Electrolysis of Copper Sulfate Solution — T . . 70 

34 — Reversible Reactions.70 

35 — Colored and Colorless Ions — T.71 


S 31 — Electrolysis of Copper Sulfate Solution (Short Method) 

— T.72 

S 32 — Electrolysis of Sodium Sulfate Solution — T . .72 

S 33 — Testing for Ions.73 

S 34 — Hydrolysis of Certain Salts.74 

Ammonia.74 

★ 36 — Preparation and Properties of Ammonia . . .74 


S 35 — Preparation of Ammonia from Various Substances . 76 

Nitric Acid — Nitrogen Oxides. 77 

37 — Preparation of Nitric Acid — T . . . . . 77 

★ 38 — Properties of Nitric Acid.78 

★ 39 — Nitric Oxide and Nitrogen Dioxide . . . .79 
















Vlll 


CONTENTS 


PAGE 

★ 40 — Test for Nitric Acid and Nitrates .... 80 


S 36 — Nitrous Oxide — T.81 

Molecular Weights .. 82 

41 — Weight of 22.4 Liters of Oxygen.82 

Sulfur. 85 

★ 42 — Different Forms of Sulfur ...... 85 

★ 43 — Sulfur Dioxide (Short Method) ..... 86 

44 — Sulfur Dioxide and Sulfurous Acid — T . . .87 

★ 45 — Properties of Sulfuric Acid.89 

★ 46 — Test for Sulfuric Acid, Sulfates, S0 4 -ions ... 90 

★ 47 — Hydrogen Sulfide (Short Method) .... 91 


S 37 — Hydrogen Sulfide — T . 92 

S 38 — Sulfides — T. 98 

Carbon — Flame. 94 

★ 48 — Distillation of Soft Coal. 94 

★ 49 — Distillation of Wood — T . . . • .95 

★ 50 — Illuminating Gas Flame — T.96 

★ 51 — Candle Flame — T. 9 ? 

★ 52 — Bunsen Burner and Flame — T .98 

★ 53 — Reduction and Oxidation with the Blowpipe . .100 


S 39 — Carbonic Acid — T.161 

S 40 — Acetylene — T.162 

Organic Compounds.103 

54 — Sugars.163 

55 — Starch.164 

56 — Testing Baking Powders.104 


S 41 — Esters.106 

S 42 — Soap.167 

S 43 — Nutrients in Food — T.108 

Bromine and Iodine.109 

S 44 — Preparation and Properties of Bromine — T . . 109 

S 45 — Bromine (Short Method).110 

S 46 — Tests for Free and Combined Bromine . . .Ill 












CONTENTS 


IX 


S 47 — Preparation and Properties of Iodine — T . 

S 48 — Iodine (Short Method) . 

S 49 — Tests for Free Iodine . 

S 50 — Tests for Combined Iodine .... 

Sodium . 

S 51 — Sodium Bicarbonate — T 
S 52 — Sodium Chloride — T . 

Calcium . 

★ 57 — Calcium Carbonate, Oxide, and Hydroxide . 

★ 58 — Hardness of Water — T . . . . 

S 53 — Tests for Calcium in Compounds 
S 54 — Properties of Cement — T . 

S 55 — Plaster of Paris — T . 

Iron . 

59 — Tests for Iron Salts . 

60 — Reduction and Oxidation of Iron Salts . 

Metals — Displacement and Tests 

★ 61 — Displacement of Metals . . . . 

62 — Flame Tests for Metals . . . . 

S 56 — Tests for Metals . 

S 57 — Tests with Borax Beads . 

S 58 — Cobalt Nitrate Tests . 

S 59 — Testing Salts for Metal and Non-Metal 
S 60 — Silver Salts and Photography — T 

S 61 — Aluminum Hydroxide . 

S 62 — Qualitative Analysis (Lead, Silver, Mercury) 

Appendix. 

Pressure of Water Vapor . 

How to Use the Bunsen Burner 
Working with Glass Tubing • 

Filtering. 

Constructing and Arranging Apparatus . 

Pouring Liquids and Transferring Solids . 


PAGE 
. 112 
. 113 

. 113 

. 113 

. 114 

. 114 
. 115 

. 116 

. 116 
. 118 

. 119 

. 120 
. 121 

. 121 

. 121 
. 122 

. 123 

. 123 
. 123 

. 124 

. 126 
. 127 

. 127 

. 128 
. 129 

. 130 

. 133 

. 133 
. 133 
. 134 

. 136 

. 137 
. 139 













CONTENTS 


X 

PAGE 

140 

Collecting Gases.^ 

Weighing. 144 

Measuring . • • .. 144 

The Metric System.. 

Smelling and Tasting. 

Accidents. 

Laboratory Supplies. 









SUGGESTIONS FOR TEACHERS 


The author does not intend that all the exercises in this 
book shall be performed by eaph pupil in the time allotted to 
a first course in chemistry. The lists given below contain the 
exercises recommended for two courses — minimum and brief, 
and should be followed without much change. The few 
exercises not included may be used to meet special needs. 

List A — Minimum Course 

This list includes the exercises for a minimum, well- 
balanced course covering a year. Essential exercises are 
starred. Exercises which should be done by the teacher 
are marked T. Supplementary exercises are marked S. 

Numbers 1, *2, *3 (or *S3), 4, S5-T, *5, *6, *7, 8-T, 
*9 (or *S8), *10 (or SlO-T), 11-T, 12 (or Sll-T), *13, *14, 

* 15, 16-T, 17-T, * 18 (A or B), S15-T, 19-T, *21 (or 20, S18), 
22 (may be omitted), *23 (or S19-T), *24 (or S22), *25, 
*26, * 27-T, *28, 29, 30-T, *31, 32-T, 33-T, S33, 34, 35-T, 
*36 (or S35), 37-T, *38, *39, *40, 41 (may be omitted), 
*42, *43 (or 44-T), *45, *46, 47, (or S37-T), *48, *49, 

* 50-T, * 51-T, * 52-T, *53, 54, 55, 56, S42, S52, 57, * 58-T, 
59, 60, *61, 62. 

List B — Brief Course 

The list includes most of the exercises in the minimum 
course together with selections from the supplementary 
exercises. Essential exercises are starred, exercises for 
teachers are marked T, and supplementary exercises are 
marked S. 


xii SUGGESTIONS FOR TEACHERS 

Numbers *1, *2, *3, S2, S4, S5-T, *5, *6, *7, S6, S7-T, 
8-T, *9, *10 (or S10-T), *11-T, *12 (or Sll-T), *13, *14, 
*15, * 16-T, *17, S13-T, *18, S14-T, S16-T, S16-T, S17-T, 
19-T, *21 (or 20), S18, 22, *23 (or S19), *24 (or S22), *25, 
*26, S21-T, S23-T, S24-T, *27-T, S25, S26, S27-T, *28, 
S28, S29, *29, 30-T, *31, 32-T, 33-T (or S31-T), S32-T, 
*S33, 34, 35-T, *36, 37-T, *38, *39, *40, 41, *42, *43 (or 
44-T), *45, *46, 47 (or S37-T and S38-T), *48, *49, *50-T, 
* 51-T, * 52-T, 53, S49-T, 54, 55, 56, S41, S42, S46, *49, 
S50, S51-T, 57, *58-T, S54-T, S55-T, 59, 60, *61, 62, S56, 
S57, S58. 











Apparatus frequently used in the laboratory 

































































































LABORATORY EXERCISES 

FOR A 

BRIEF COURSE IN CHEMISTRY 

GENERAL DIRECTIONS FOR THE PUPIL 

1. Apparatus. — The apparatus frequently used is shown 
in the figure on the opposite page. 

A — Thistle tube. B — Test tube holder. C — Glass 
plate. D — Pinch clamp. E — Glass tube. F — Crucible 
block. G — Porcelain crucible (covered). H —Triangle. 
I — Forceps. J — Blowpipe tube. K — Test tube brush. 
L — Blowpipe. M — Right-angle bend. N — Glass rod. 
0 —Porcelain evaporating dish. P —Glass plug. Q —Mor¬ 
tar and pestle. R — Rubber stopper (2-hole). S — Bottle. 
T —Deflagrating spoon. U —Rubber stopper (1-hole). 
V — Erlenmeyer flask. W — Iron clamp. X — Wire gauze. 
Y —Iron ring. Z —Iron stand. AA — Funnel. BB —Test 
tube (small). CC — Test tube (large). DD — Graduated 
cylinder. EE — Beaker. FF — Test tube rack (in part). 

Use this figure to identify the unfamiliar apparatus in your 
desk. When your set of apparatus agrees with the list, sign 
and hand the completed list to the Teacher. 

Some general apparatus, e.g. scales, is kept in the labora¬ 
tory, and special apparatus will be supplied as needed. 

Besides the apparatus in your desk, you will need a rubber 
apron and a pair of sleeves, or something similar, to protect 
your clothes. 


1 


2. Laboratory notebook. — You will need a laboratory 
notebook. Write your name and the number of your desk 
on the cover of the notebook. In this book you should keep 
a neat and accurate account of all the laboratory exercises 
you perform. In general, your record should include : — 

(1) The number and title of the exercise and the date. 

(2) A brief account in your own words of the exercise as you 
did it. 

(3) Answers to all questions — not merely yes or no, but a 
brief answer based on your own work. 

(4) Answers or records by the numbers and letters which 
correspond to those in the directions, e . g . 1, I, (1), ( a ), etc. 

(5) All numerical data, e . g . weights and volumes, in the 
form required by the directions. 

(6) Equations wherever they are asked or will make the 
notes clearer. 

(7) A simple sketch of the apparatus (if time permits). 

3. Doing laboratory exercises. — To do laboratory exer¬ 
cises successfully, you must meet certain requirements. 

(1) Before the laboratory period find out what exercises 
are to be done, read the directions carefully, and plan the 
work as well as you can. 

(2) When you enter the laboratory, open your desk at 
once, or have it opened, take out the necessary apparatus, 
and begin to work without delay. 

(3) When you are doing an exercise in the laboratory, 
follow the directions carefully, especially about quantities of 
chemicals, heating, and weighing; work and think inde¬ 
pendently. If you need assistance, ask the Teacher. 

(4) Learn as soon as possible: 

(а) The name of each piece of apparatus, and how to use it. 

(б) How to perform skillfully the operations frequently 
done in the laboratory (see Appendix §§ 2, 4, 5, 6, 7, 8). 

(c) How to set up apparatus quickly and correctly. 

(i d ) How to do arithmetical work rapidly and accurately, 
and to check results. 

(5) Before you leave the laboratory, be sure your apparatus 
is clean and put away, the water and the gas are turned off, 
and your desk is clean. 


2 


LABORATORY EXERCISES 


PROPERTIES — CHEMICAL CHANGE — 
MIXTURE — COMPOUND 

Exercise 1 — Properties and Chemical Change 

Materials. — Sulfur, magnesium ribbon. 

Apparatus. — Block of wood, forceps, Bunsen burner. 

(a) Examine a piece of sulfur. Note its properties, espe¬ 
cially the color. Put a small piece on a block of wood and 
heat it with a flame. Observe at once how the sulfur be¬ 
haves; note especially the color of the flame. Note very 
cautiously the odor of the product by brushing a little gently 
toward the nose. Then extinguish the flame by pressing 
a piece of paper .upon the burning 
sulfur. 

( b ) Examine a piece of mag¬ 
nesium ribbon. Note its color, 
appearance ( e.g . luster), and flexi¬ 
bility. Grasp one end with the 
forceps, and hold the other end 
in the hottest part of the Bunsen 
flame until the magnesium under¬ 
goes a definite change (Fig. 1). 

Remove at once and examine the product. Compare with 
unheated magnesium as to color, luster, and flexibility. 

Write in your laboratory notes the properties of ( a ) sulfur 
and ( b ) magnesium. 

Write also the evidence of chemical change when (a) sulfur 
and (6) magnesium are heated. 

3 







Optional Exercises 

1. State one conspicuous property of sulfur. Of 
magnesium. 

2. How does this exercise illustrate chemical change? 

^Exercise 2 — Mixture and Compound 

Materials. — Powdered sulfur, powdered iron (or clean, fine iron 

filings), dilute hydrochloric acid, carbon disulfide. 

Apparatus. —Scales, magnet, lens, test tubes and holder, Bunsen 

burner, mortar and pestle. 

A. Weigh about 4 gm. of powdered sulfur on a piece of 
paper on the scales (see Appendix, § 8). Weigh about 7 gm. 
of powdered iron (or clean, fine iron filings) on another 
paper. 

(а) Note and record their conspicuous properties. Try 
the effect of a magnet on each by moving it along the under 
side of the paper. Note each result. 

(б) Put a pinch of each in separate test tubes, add a little 
dilute hydrochloric acid, and warm gently. Note the result 
in each case, especially the odor, if any, of the gas from the 
tube containing the iron. 

(c) Put a pinch of each in separate test tubes, add about 
5 cc. of carbon disulfide, and shake well. (Caution. Carbon 
disulfide catches fire readily. Do not use carbon disulfide 
near a flame.) Note the result, especially in the tube 
containing the sulfur. 

B. Mix the rest of the sulfur and iron thoroughly by 
grinding them together in a mortar. Divide the mixture into 
two equal portions. Use one in (a) and the other in ( b ). 

(a) Examine the mixture with a lens, and note if you can 
detect sulfur and iron. Try the effect of a magnet on some 
of the mixture, and note the result. 

Divide this portion into two parts. (1) Put one part in 
a test tube, and add dilute hydrochloric acid. Warm the 
acid mixture gently until there is evidence of action, note 
the odor and compare with the odor from the iron and acid 
in A ( b ). (2) Put the other part in a test tube, add 5 cc. of 

carbon disulfide, shake well, let it settle, pour the liquid 

4 


into a dish, and stand the dish in the hood. When the carbon 
disulfide has evaporated, examine the solid product, and 
decide what it is. 

(b) Put the other half of the mixture from B in a test tube, 
attach the holder, and heat (Fig. 2) until the mass begins to 
glow, then take the test tube 
out of the flame. Heat again 
intensely for a few minutes. 

Let the tube cool, hold it over 
the mortar, and break off the 
lower end with the pestle. Re¬ 
move the product, and use it 
in (c). 

( c ) Examine the product from 
( b ) with a lens, and note if iron Fig. 2. — Heating a mixture of 
or sulfur is detected. Try the 11011 and sulfur in a test tube 
effect of a magnet on a piece (from the outside), and note 
the effect. 

Put a piece in a test tube, add a little hydrochloric acid, 
note the odor of the gas, and pour the contents immediately 
into a waste jar in the hood. Compare the odor of the gas 
with similar tests. Conclude as to the presence of (1) iron, 
or (2) a new substance. 

Put a piece in another test tube, add 5 cc. of carbon 
disulfide, and shake well. As soon as the solid has settled, 
pour the liquid into a dish, stand the dish in the hood, and 
let the liquid evaporate. Note if any sulfur is left in the 
dish. Conclude as to the presence of sulfur in the product. 

Write a brief account of this exercise in your laboratory notes , 
stating clearly how this exercise shows the difference between a 
mixture and a compound. 

Optional Exercises 

1. What are some characteristics of a mixture? Of a 
compound ? 

2. Is the product in B (6) a mixture or a compound? 

Why? 



5 







SUPPLEMENTARY EXERCISE ON COMPOUNDS 


Supplementary Exercise 1 — Decomposition of Mercuric 

Oxide 

Materials. — Mercuric oxide, joss stick (or small splint of wood). 
Apparatus. — Test tube clamped to iron stand (Fig. 3). Bunsen 
burner. 

Put a little mercuric oxide on the end of a narrow piece of 
paper creased lengthwise, and slip the powder into a test 
tube (Figs. 4, 5). The powder 
should nearly fill the round end of 
-\ the test tube. Hold the test tube 




3 “ 


Fig. 3. — Apparatus for de¬ 
composing mercuric oxide 



Fig. 4. —Putting a powder into a test tube 
— first step 


in a horizontal position, shake it to spread the powder into 
a thin layer, and then clamp the test tube as in Fig. 3. 

(a) Heat the test tube 
gently at first; then heat 
intensely the part that con¬ 
tains the substance. After 
heating for several minutes 
insert a glowing joss stick 
well into the test tube. Ob¬ 
serve the change in the joss 
stick. The change is due to 
oxygen. If there is no change, 
heat intensely and again in¬ 
sert the glowing joss stick. 

Fig. 5. - Putting a powder into a , ( 6 ) Examine the deposit on 
test tube—second step the upper part of the tube. 
















Conclude what it is. If you are in doubt, scrape out a little 
upon a piece of paper and examine it. (Note. — Some 
unchanged mercuric oxide will probably be left; throw it in 
the waste jar.) 

Write in your laboratory notes a brief account of this exercise. 


Optional Exercises 

1. To what class of substances does mercuric oxide belong ? 

2. To what class does the product from (a) belong? 
From (6)? 

3. Into what substances can mercuric oxide be decom¬ 
posed ? 

OXYGEN 


^Exercise 3 — Preparation and Properties of Oxygen 

Materials. — 5 gm. of potassium chlorate, 5 gm. of manganese 
dioxide, joss stick, sulfur, piece of charcoal fastened to one end 
of a copper wire (30 cm. long), wad of iron thread (“steel wool”)* 
Apparatus. — As in Fig. 6. A is a large test tube (20 cm. or 8 in.) 
provided with a one-hole rubber stopper, to which is fitted a 
short glass tube B ; the latter is connected by the rubber tube C 
with the delivery tube D. E is a r 

pneumatic trough with a support for 
the collecting bottle F. 

I. Preparation. — Weigh the po 
tassium chlorate on the scales on a 
piece of paper 
creased length¬ 
wise, and slip it 
into the test 
tube; do the 
same with the 
manganese di¬ 
oxide. Shake 
the test tube until the chemicals are thoroughly mixed. 
Hold the test tube in a horizontal position and roll or shake 
it until the mixture is spread along about one half of the 

7 



Fig. 6. —Apparatus for preparing oxygen 


















Fig. 7. — Inverted 
bottle full of water 


tube. Insert the stopper with its tubes, and clamp the 
test tube to the iron stand, as shown in Fig. 6. The end 
of the delivery tube D should rest on the bottom of the 
trough under the hole in the support. 

Add water to the pneumatic trough E until the hole in 
the support is covered. Fill one bottle full of water, cover 
it with a piece of filter paper, invert it (Fig. 7), lower it into 
the water in the trough, remove the paper, 
and stand the inverted bottle F upon, or 
near, the support. Fill two more bottles 
and have them ready to replace the one in 
the trough. 

Heat the test tube gently with a small 
Bunsen flame (about 10 cm. (4 in.) high). 
Move the flame slowly along the test tube, 
taking care not to heat the tube too long 
in one place nor too near the rubber stopper. As soon as the 
gas bubbles regularly through the water, slip the inverted 
bottle over the hole in the support. The gas will rise in the 
bottle and force out the water. If the gas comes off too 
rapidly, remove the flame for an instant; if too slowly, in¬ 
crease the heat; if not at all, examine the stopper and the 
rubber connecting tube for leaks, and adjust accordingly. 

When the first bottle is full of gas, remove it, stand it 
(mouth upward) upon the desk, and cover it tightly with a 
piece of filter paper. Invert another bottle in the trough, 
remove the paper, and slip the bottle over the hole. Fill 
it with oxygen. Fill the other bottle in the same way. As 
soon as the last bottle of gas has been collected, immediately 
remove the end of the delivery tube D from the water. 
(Note. — Save the test tube A and contents for Supple¬ 
mentary Exercise 2.) Perform II at once. 

II. Properties. — (a) Thrust a glowing joss stick into one 
bottle, and observe the result. Remove the joss stick, 
make it glow again, and repeat. Note (1) how the glowing 
joss stick changes, and (2) whether oxygen burns. Use this 
bottle of gas for (6). 

( b ) Put a small piece of sulfur in the deflagrating spoon, 
and heat it until the small, blue flame of burning sulfur is 

8 



seen. Then lower the spoon into the bottle of oxygen. 
Observe any change in the flame. Very cautiously waft a 
little of the contents of the bottle toward the nose and note 
the odor. 

Remove the spoon and plunge it into the water in the 
trough to extinguish the burning sulfur. Fill the bottle 
one-fourth full of water, cover with the hand, and shake well. 
Cork tightly, and save for Supplementary Exercise 2. 

(c) Heat the charcoal (fastened to the wire) long enough 
to produce a faint glow, then lower it into a bottle of oxygen. 
Observe the result. 

Add limewater (about 10 cc.) to the bottle, shake well, 
and save as in (6). 

( d ) Twist one end of the copper wire (used in (c)) firmly 
around the wad of iron thread, heat the ends of a few strands 
for an instant, and quickly lower it into a bottle of oxygen. 
The iron should change conspicuously. Observe the result. 

Write in your laboratory notes (1) a very brief account of I 
and (2) brief statements of the observations made in II. 

Optional Exercises 

1. State some physical properties of oxygen, e.g. color, 
solubility in water. 

2. State the chemical conduct of oxygen. 

3. What is the test for oxygen ? 

4. Sketch the apparatus used to prepare oxygen. 

Exercise 4 — Heating a Known Weight of a Metal in Air 

Material. — Zinc dust. 

Apparatus. — Crucible block (Fig. 8), crucible (Fig. 9), balance, 
weights, triangle, iron stand and ring. 

Copy the form of Record (see below) in your laboratory 
notes. When you weigh, take the book, or sheet, containing 
this Record to the balance (or scales) and enter all weights 
in the proper place as soon as the weighing is made. 

9 


Clean and dry a porcelain crucible and cover. Place the 
covered crucible on the crucible block (Fig. 8), and carry it 
to the balance (or scales); always 
use this block in carrying the cruci¬ 
ble to and from the balance (or 
scales). Weigh the covered crucible 
(ask for directions or follow direc- 
Fig. 8. - Block for carrying tions in APPENDIX, § 8). Enter the 
a crucible weight in the Record. 




Record 

Wt. of covered crucible and zinc ...... 

Wt. of covered crucible. 

Wt. of zinc. 

Wt. of covered crucible and contents after heating 

Wt. of covered crucible. 

Wt. of contents after heating. 

Wt. of zinc. 

Change in weight. 


gm. 

gm. 

gm. 

gm. 

gm. 

gm. 

gm. 

gm. 


Obtain about 3 gm. of zinc dust on a slip of paper creased 
lengthwise, and slide it into the crucible. Weigh the 
covered crucible and zinc accurately. 

Enter the weight in the Record. 

Place the covered crucible on the tri¬ 
angle supported by a ring on an iron 
stand as shown in Fig. 9. Heat gently 
with a low flame for a minute or two, then 
increase the heat until the flame is just 
above the middle of the crucible. Heat 
for about fifteen minutes. Occasionally 
lift the cover for an instant by grasping 
the ring firmly with the forceps. 

Let the crucible cool. Weigh it. Enter 
the weight, and complete the Record. 

Show the completed Record to the 
Teacher before throwing away the contents 
of the crucible. (Note. — The crucible, if blackened, can 
be cleaned by warming a little dilute hydrochloric acid in it.) 

10 



Fig. 9. —Covered cru¬ 
cible on a triangle 





















Optional Exercises 

1 . What is the result of heating a known weight of a metal 
in air? 

2. To what is the difference in weight due? 

3. What is the name of the product? 

4. Complete : Zinc H-=-. 

SUPPLEMENTARY EXERCISES ON OXYGEN 

Supplementary Exercise 2 — Examples of Chemical Change 
in Exercise 3 

Materials. — Contents of test tube A and of the bottles from 
Exercise 3, II ( b ), (c); potassium chlorate (pure) and silver 
nitrate solutions, litmus paper (blue). 

Apparatus. — Funnel, filter paper. 

(а) Add 15 cc. of water to the test tube (from Exercise 3, 

I), warm gently to loosen the contents and dissolve the 
soluble material. Filter (ask directions or follow directions 
in Appendix, § 4). (1) To a few cc. of the filtrate (the 

liquid that went through the filter paper) add a few drops of 
silver nitrate solution, and observe the result. The solid 
product is silver chloride, and is always formed when silver 
nitrate and any chloride (in this case potassium chloride) 
interact. (2) Now add silver nitrate solution to (pure) 
potassium chlorate solution, and observe the result. Com¬ 
pare with (1) and note the difference. 

(б) Heat strongly a part of the black substance left on the 
filter paper as in Supplementary Exercise 1, and test for 
oxygen. Note if oxygen is given off. Compare the rest of 
the black substance with a sample of the manganese dioxide 
used in Exercise 3 and see if they are apparently the same. 

In your laboratory notes write answers to these questions. 
(1) W hat chemical change tookplace in Exercise 3,1? (2) What 
is the verbal equation for the change f (3) The chemical 
equation? (4) From what compound did the oxygen come in 

Exercise 3, I? 


11 



(c) Dip a glass rod into the liquid saved from Exercise 3, 
II (6), touch a piece of blue litmus paper with the moistened 
end, and observe the change in color. This change is caused 
by acids; in this case by sulfurous acid (H 2 S0 3 ) which was 
formed by the uniting of sulfur dioxide (S0 2 ) and water. 

(i d ) Shake the bottle saved from Exercise 3, II (c) and note 
the cloudiness of the liquid. Recall that both liquids at 
first were clear. The cloudiness is caused by particles of 
insoluble calcium carbonate suspended in the liquid. The 
calcium carbonate (CaC0 3 ) is formed by a reaction between 
carbon dioxide and limewater, which is a solution of calcium 
hydroxide (Ca(OH) 2 ). 

In your laboratory notes write answers to these questions. 
(1) What is (a) the verbal and (b) the chemical equation for 
the formation of sulfur dioxidef (2) Of carbon dioxidet 
(3) Of sulfurous acidt (4) Of calcium carbonate f 

Optional Exercises 

1. What is the test for sulfur dioxide? 

2. What is the test for carbon dioxide ? 

3. How would you distinguish a chloride from a chlorate ? 

4. Complete : (a) S0 2 H-= H 2 S0 3 ; (b) C0 2 + - 

= CaC0 3 . 

5. State the completed equations in 4 in your own words. 

Supplementary Exercise 3 — Preparation and Properties of 
Oxygen (Short Method) 

Materials. — Lead dioxide, potassium chlorate, sodium peroxide, 
hydrogen peroxide, dilute sulfuric acid, potassium permanganate 
solution, joss stick. 

Apparatus. — Test tube and holder (Fig. 2), burner. 

(a) Put a little lead dioxide into a test tube as shown in 
Figs. 4 and 5. Attach the holder, and heat gently (Fig. 2). 
After a short time, test for oxygen by putting a glowing joss 
stick into the tube near (but not touching) the substance. 
Note the effect on the glowing joss stick. 

12 




(I b ) Proceed as in (a), using potassium chlorate. Note 
the result. 

(c) Fill a test tube nearly full of water and stand it in the 
test tube rack. Obtain a little sodium peroxide (Care!) 
on a creased paper, cautiously slip the sodium peroxide into 
the water, and quickly put a glowing joss stick into the gas 
in the upper part of the test tube. Note the result. 

(d) Fill a test tube half full of fresh hydrogen peroxide, 
add half the volume of dilute sulfuric acid, shake, and then 
nearly fill the test tube with potassium permanganate solu¬ 
tion. Immediately test the escaping gas with a glowing 
joss stick. Note the result. 

Write a brief account of this exercise in your laboratory notes, 
stating a conspicuous property of oxygen. 

Supplementary Exercise 4 — Preparation of Copper Oxide by 
Heating Copper in Air 

Material. — Copper borings. 

Apparatus. — Evaporating dish, test tube fitted with a cork. 

Put about 4 gm. of clean copper borings in an evaporating 
dish and stand the dish on a gauze-covered ring attached to 
an iron stand (Fig. 10). Heat the dish 
carefully but intensely about ten minutes. 

Then heat for five minutes by holding 
the flame directly upon the contents of 
the dish. Note the marked change in 
the copper. 

When the dish is cool, transfer the con¬ 
tents to a test tube, cork tightly, and save 
for Exercise 10. (Note. — The dish can 
be cleaned by warming dilute nitric acid 
in it.) 

Write answers to these questions in your 
laboratory notes. (1) What is the chemical 
name and formula of the compound formed f 
(2) What elements combined t (3) What general name is given 
to this kind of chemical change ? (4) What special name f 

13 



ing dish on a gauze- 
covered ring 








Supplementary Exercise 5 — Slow and Rapid Oxidation — 
Teacher’s Exercise 

Materials. — Powdered potassium nitrate, charcoal, phosphorus- 
tipped match, bottle of oxygen, iron filings (free from oil), phos¬ 
phorus (for ( d )), magnesium ribbon (for ( e )), bottle of oxygen 
(for (e)). 

Apparatus. — As in Fig. 11, iron pan (or brick). 

Caution. — See ( d ). Special care must be taken in all 
exercises in which phosphorus is used. The substance 
oxidizes so quickly in the air that it often takes fire un¬ 
expectedly. To prevent its oxidation it is 
kept under water. It is dangerous to 
handle, since the burns made by it are 
deep and painful. 

(a) Construct an apparatus as shown in 
Fig. 11. Wet the inside of the test tube A, 
drop in clean iron filings, and roll the test 
tube to make the filings stick. Insert the 
stopper with the long tube B, invert, and 
clamp the test tube A to the iron stand so 
that the open end of the tube B is just 
above the bottom of the dish filled with 
water (Fig. 11). Let the whole apparatus 
stand undisturbed for an hour or two. 
Then note the height of the water in the 
long tube. 

(b) Lay a piece of charcoal on an iron 
pan (or brick), heat it with a direct flame, 
and when hot, cautiously sprinkle powdered 
potassium nitrate upon the hot surface. 
As the chemical action begins, continue to 
sprinkle on the potassium nitrate. Observe 
the action, especially its violence and 

rapidity, also the effect on the charcoal. 

(c) Rub the head of a phosphorus-tipped match with the 
finger in a dark place, and note the result. 

(d) See Caution. Lift a piece of phosphorus from the 
bottle with the forceps, put it in an evaporating dish nearly 

14 



Fig. 11.—Apparatus 
for showing slow 
oxidation 













full of water, cut off a thin slice with a sharp knife, return the 
rest of the phosphorus to the bottle, and place the slice on an 
iron pan (or a brick). Stand well back, and observe the result. 

(e) Grasp one end of a short piece of magnesium firmly 
with the forceps, hold the Other end in the flame for an in¬ 
stant, then remove it, and let the magnesium burn in the air. 

In a similar way light another piece and quickly thrust 
it into a bottle of oxygen. Compare the results. Note in 
which case oxidation was more rapid. 

Write in your laboratory notes a brief account of this exercise. 
Write also answers to these questions. (1) In (a) what 
caused the water to rise in B? (2) In what parts of this 
exercise was little heat liberated f Considerable heat t Why f 
(3) What is the name and the formula of the oxides produced 
in (6), (c), (d), (e)f 

CARBON 

^Exercise 5 — Properties of Charcoal 

Materials. — Wood charcoal (lump), animal charcoal, test wire, 
(see Fig. 22 and Appendix, § 5 (d)) crucible, vinegar, hydrogen 
sulfide solution. 

Apparatus. — Test tube fitted with a cork, crucible and support. 

A. Wood Charcoal. — Wind the end of a test wire around 
a piece of charcoal, hold it in the flame, and observe the 
result, especially the ease or difficulty of ignition, presence or 
absence of flame and smoke, formation of ash. 

B. Animal Charcoal. — (a) Cover the bottom of a crucible 
with animal charcoal, stand the crucible on a triangle and 
heat intensely for about half an hour. (Meanwhile do ( b ), 
(c).) Examine the residue. Note the color. Compare 
with a sample of the original charcoal. 

( b ) Fill a test tube one-fourth full of powdered animal 
charcoal (refer to Figs. 4, 5). Add 10 cc. of hydrogen sulfide 
solution, and cork securely. Shake well. After ten minutes, 
remove the stopper and smell of the contents. Note if the 
odor is much less offensive. Conclude what property of 
animal charcoal this exercise illustrates. 

15 


(c) Fill a test tube one-fourth full of powdered animal 
charcoal (refer to Figs. 4, 5), add 10 cc. of vinegar, shake 
thoroughly, and then warm gently. Filter through a wet 
paper. Compare the colors of the filtrate and the original 
vinegar. Conclude what property of animal charcoal this 
exercise illustrates. 

Write a summary of the properties of charcoal in your labora¬ 
tory notes. 


^Exercise 6 — Reduction of Copper Oxide by Carbon 

Materials. — Powdered copper oxide, powdered wood charcoal, 
calcium hydroxide solution. 

Apparatus. — As in Fig. 12, lens. 

Grind together in a mortar about 5 gm. of copper oxide 
and 1 gm. of powdered wood charcoal. Put the mixture on a 
creased paper (refer to Figs. 4, 5) 
and slip it into the test tube A. 
Fill the bottle B half full of calcium 
hydroxide solution. Arrange the 
apparatus as in Fig. 12. 

Heat the test tube gently at 
first, and adjust the height so the 
gas will bubble through the calcium 
hydroxide in B. Heat intensely 
for about ten minutes, moving the 
burner along the part of the test 
tube that contains the mixture. 
Observe the change in the calcium 
hydroxide. 



Fig. 12. — Apparatus for reduc¬ 
ing copper oxide with carbon 


As soon as a definite change is noted in B, remove the end 
of the delivery tube from B, and stop heating. Let the 
test tube cool and pour the contents into a mortar. Examine 
carefully with the eye and with a lens. Note another 
substance besides carbon. 


Write in your laboratory notes an interpretation of the 
chemical change in A and in B, in (a) words and ( b ) chemical 
equations. 


16 










^Exercise 7—Preparation and Properties of Carbon Dioxide 


Materials. — Calcium carbonate, dilute hydrochloric acid, candle 
fastened to a wire, joss stick, calcium hydroxide solution. 

Apparatus. — As in Fig. 13. A is a 250 cc. bottle provided with 
a two-hole stopper, through which passes the dropping tube B 
and the right-angle 
bend C ; the tube D 
(15 cm. or 6 in.) is 
attached to the bent 
tube by the rubber 
tube E. 

Instead of the ap¬ 
paratus shown in Fig. 

13, one of the simple 
forms shown in Fig. 

14 may be used; in 
these the lower end of 
the thistle tube must 
be beneath the acid. 



Fig. 13. 


Apparatus for preparing carbon 
dioxide 


The dropping tube is made as follows: Cut off the top of 
a thistle tube about 2.5 cm. (1 in.) below the juncture of the 
stem and cup, and heat the sharp ends a minute or two in the 
flame ; when cool, slip a thick-walled 
rubber tube (5 cm. or 2 in. long) 
over one end of the stem, attach a 
pinch-clamp to the rubber tube, and 
connect the tube with the cup, tak¬ 
ing care to have the ends of the 
glass tubes as close together as possi¬ 
ble. If properly constructed, the 
cup will remain upright when full 
of liquid. 

I. Preparation. — Put about 
20 gm. of calcium carbonate into the 
bottle A, and arrange the apparatus 
as in Fig. 13. Fill the pneumatic trough with water, fill a 
bottle with water, cover with filter paper (Fig. 7), invert, 
stand it on the support, and remove the paper. Fill three 
other bottles and have them ready. 

17 



Fig. 14. — Simple apparatus 
for preparing carbon dioxide 

































Introduce enough dilute hydrochloric acid through the 
dropping tube B to cover the calcium carbonate. Carbon 
dioxide will be evolved at once. Collect four bottles, cover 
tightly with filter paper, and stand aside till needed. Pro¬ 
ceed at once with II. 

II. Properties. — (a) Plunge a blazing joss stick into a 
bottle. Observe the effect on both gas and joss stick. 

( b ) Lower a short, lighted candle into a bottle of air, and 
quickly invert a bottle of carbon dioxide over it, holding 
the bottles mouth to mouth. Observe the effect on the 
candle. 

(c) Pour a little calcium hydroxide solution into a bottle of 
carbon dioxide, cover with the hand, and shake vigorously. 
Note the effect on the calcium hydroxide. This is the usual 
test for carbon dioxide. 

(d) Invert a bottle of carbon dioxide in the pneumatic 
trough, and shake vigorously, keeping the mouth beneath 
the water. Observe the result (inside the bottle). 

Note. — As soon as ( d ) is performed wash the acid from 
the marble and save the solid for other exercises. 

Write a brief account of I in your laboratory notes. 

Write also answers to these questions. (1) What do II (a) 
and (6) show about the relation of carbon dioxide to combustion t 
(2) What does II ( b ) show about the relative weights of carbon 
dioxide and air? (3) What does II (d) show about the solu¬ 
bility of carbon dioxide ? 

Write also a statement of the test for carbon dioxide , including 
the ( a ) verbal equation and (b) chemical equation. 

Exercise 8 — Carbon Monoxide — Teacher’s Exercise 

Materials. — Oxalic acid, calcium hydroxide solution. 

Apparatus. — As in Fig. 15. 

Caution. — Carbon monoxide and oxalic acid are poison¬ 
ous. Hot sulfuric acid is dangerous. Perform this exer¬ 
cise in the hood with unusual care. 

I. Preparation. — Put 10 gm. of oxalic acid in the flask A 
(Fig. 15), and add 25 cc. of concentrated sulfuric acid. Put 

18 


enough calcium hydroxide solution in B to cover the end of 
the tube E. Arrange the apparatus as in Fig. 15. 

Heat the flask A gently, and carbon monoxide will be 
evolved. Collect all the gas, but do not use the first bottle, 
covering the bottles with glass plates as 
they are filled, and setting them aside 
temporarily. When the last bottle has 
been collected and covered, loosen the 
stopper in B, and remove the end 
of H from the water in the trough. 

Proceed at once with II. j 

II. Properties. — (a) Note 
that the gas is colorless. 

(6) Hold a 
lighted match at 
the mouth of a 
bottle. Note the 
flame, especially 
its color. After 
the flame has dis¬ 
appeared, drop 
a lighted match into the bottle. Note the result. Draw a 
conclusion and verify it by (c). 

(c) Burn another bottle of gas, note the flame again, and 
after the flame has disappeared, pour calcium hydroxide 
solution into the bottle and shake. Note the result. 

Write in your laboratory notes (1) a brief description of the 
preparation of carbon monoxide and (2) a summary of the 
observed properties of carbon monoxide. 

Write also answers to these questions. (3) What gas besides 
carbon monoxide was produced in I ? (4) What are the equa¬ 

tions for I, II ( b) and ( c) f 



Fig. 15. — Apparatus for preparing carbon monoxide 


Optional Exercises 

1. How could carbon monoxide be detected in (a) the 
smoke from a fire, and (6) the exhaust gases from an auto¬ 
mobile ? 

2. Complete : (a) C + C0 2 =- 

19 


; (6) C0 + 0 2 = 























SUPPLEMENTARY EXERCISES ON CARBON DIOXIDE 

Supplementary Exercise 6 — Combustion and Carbon 
Dioxide 

Materials. — Copper wire, charcoal, limewater, candle, wood, 
paper, denatured alcohol, gasolene. 

Apparatus. — Bent tube as in Fig. 17 for (<7). 

(a) Wind one end of a copper wire around a small lump of 
charcoal, hold it in the flame until the edges glow, and then 
lower it into a bottle. Let it remain 



bottle and then test.) 

(e) Proceed as in (d), using gasolene (Care !) instead of 
alcohol. Note the result. (See Note in (d).) 

(/) Hold a bottle over a low Bunsen flame for a minute or 
so, and then test as in (a). Note the result. 

20 












(g) Exhale the breath through a glass tube into a bottle 
half full of limewater (Fig. 17). Describe the result. Con¬ 
clude what gas the breath contains. 

Write briefly the results of this exercise in your laboratory 
notes. 

Write also answers to these questions. (1) Is carbon dioxide 
a product of combustion in each case f (2) What are two tests 
for carbon in a compound f 


Supplementary Exercise 7 — A Fire Extinguisher and 
Carbon Dioxide — Teacher’s Exercise 

Materials. — Dilute sulfuric acid, saturated sodium bicarbonate 
solution. 

Apparatus. — Bottle with one-hole stopper and tubes as in Fig. 18. 

Make a simple extinguisher like that shown in Fig. 18. 
The bottle and tubes are those used (as A-C-E-D ) in the 
apparatus shown in Fig. 13. The bottle is filled about 
two-thirds full with saturated 
sodium bicarbonate solution. 

The small tube (inside the 
bottle) contains dilute sulfuric 
acid and a piece of lead to 
hold it down after it is lowered 
into the solution. Connect 
the tubes with the stopper and 
push the stopper well down 
into the neck of the bottle. Fig. 18 . —Simple fire extinguisher 
Build a small fire in a dish 

or on some bricks. Hold the end of the tube in one hand, 
with the other grasp the bottle by the neck, taking care to 
hold the stopper tightly with the fingers, invert the bottle, 
and direct the stream upon the fire. 

Write answers to these questions in your laboratory notes. 
(1) Why are sulfuric acid and sodium bicarbonate used in a 
fire extinguisher ? (2) Why does the liquid flow out of a fire 

extinguisher with such force t 



21 








HYDROGEN 


^Exercise 9 — Preparation and Properties of Hydrogen 

Materials. —10 gm. of granulated zinc, dilute sulfuric acid, 
copper sulfate solution, wax taper. 

Apparatus. — As in Fig. 19. See also Fig. 20 for optional forms. 


I. Preparation. — Slip the zinc into the bottle (or test 


tube) 


Fig. 19. Insert the stopper with its tubes. If one 
of the optional forms (Fig. 20) is used, the thistle 
tube must dip beneath the surface of the acid. Be 
sure there are no leaks. Fill the pneumatic trough 

with water as usual, 



ap- 

the 


Fig 


Apparatus for preparing hydrogen 


and adjust the 
paratus so that 
end of the delivery 
tube rests on the bot¬ 
tom of the trough 
under the hole in the 
support. Fill the 
bottles with water, 
and covSr each with 


U 


r 


Fig. 19). 

u 




the filter paper; invert one in the trough, remove the paper, 
and stand the inverted bottle upon the support 

Put 2 or 3 cc. of copper sulfate 
solution in the cup, fill with dilute 
sulfuric acid, and let the acid mix¬ 
ture run into the bottle by pinching 
the clamp ; if the acid does not flow 
freely down the tube into the bottle, 
loosen the stopper for an instant. 

(The copper sulfate hastens the 
chemical change.) The gas will 
bubble through the water up into 
the bottle. 

Collect and remove four bottles of 
gas as in the Preparation of Oxygen 
(Exercise 3), taking care to cover each bottle tightly with 
a piece of wet filter paper. If the evolution of gas slackens 

22 




s~ 


Fig. 20. — Optional appa¬ 
ratus for hydrogen 
































or ceases, add a little more acid through the dropping 
tube. 

Save the contents of the generator bottle (or test tube) for 
Supplementary Exercise 9. Perform II at once. 

II. Properties. — (a) Uncover a bottle for an instant to 
let a little air in, and then hold a lighted match at the mouth 
of the bottle. Observe the result. 

(b) Remove the paper from another bottle and allow it to 
remain uncovered for three minutes — by the clock. Then 
show the presence or absence of hydrogen by holding a 
lighted match at the mouth of the bottle. Observe the 
result. 

(c) Stand a covered bottle of hydrogen on the desk, 
place a bottle of air over it, remove the paper, and bring the 
mouths of the bottles together. Let them remain in this 
position for a minute or two, then remove the upper bottle 
and cover both with wet filter paper. 

Remove the paper from one bottle and hold a lighted 
match at the mouth. Observe the result. Do the same with 
the other bottle. 

(d) (Read directions carefully.) Invert a covered bottle 
of hydrogen, remove the paper, and quickly thrust a lighted 
taper up into the bottle. Withdraw the taper slowly. Then 
insert and withdraw it several times, and observe carefully 
(1) if the hydrogen burns, (2) if so, where, and (3) if the taper 
burns both inside and outside the bottle. Feel of the neck 
of the bottle and note the result. 

Note. — As soon as II is completed, wash the zine thor¬ 
oughly with water several times, and save it for other 
exercises. 

In your laboratory notes write (1) a very brief account of 
Exercise 9, I and (2) brief statements of the observations made 

in II. 


Optional Exercises 

1. What property of hydrogen is shown by II (&)? By 
II (c)? 

2. As in 1, what properties by II (d) ? 

23 


3. State the conspicuous physical properties of hydrogen. 

4. What is a test for hydrogen? 

5. Why was there a marked explosion in (a) ? Why none 
in(d)? 

6. Does hydrogen support combustion? Compare with 
oxygen. 

7. Sketch (from memory, if possible) the apparatus used 
to prepare hydrogen. 

^Exercise 10 — Reduction of Copper Oxide by Illuminating 

Gas 

Materials. — 5 gm. of copper oxide (or the copper oxide saved 
from Supplementary Exercise 4). 

Apparatus. — As in Fig. 21. 

Arrange the apparatus as in Fig. 21. A is a large test 
tube. B is a piece of rubber (burner) tubing tightly con¬ 
nected with a piece of glass tubing which passes through a 
one-hole stopper. Clamp the stopper to the stand so that the 

free end of the glass 
tube is slightly raised. 
Connect the free end of 
the rubber tube to the 
illuminating gas supply. 

Turn on the gas, light 
it at the end of the 
glass tube, and regu¬ 
late the flame so that 
it is about 2 cm. (nearly 
1 in.) long. 

Put the copper oxide 
in the test tube A, hold 
it horizontal and tap it 
to spread out the solid. Then pinch the tube to extinguish 
the gas, and slip the test tube over the glass tube as shown 
in the figure. Light the gas at the mouth of the test tube 
and let it burn. 

Heat gently the end of the test tube containing the copper 
oxide. Observe (1) the change in the solid and (2) the deposit 

24 



Fig. 21. — Apparatus for reducing copper 
oxide by illuminating gas 



















on the cooler part of the test tube. Pinch the rubber tube 
and turn off the gas. 

Write answers to these questions in your laboratory notes. 
(1) In what way was the solid changed (a) physically and 
( b) chemically? (2) What was the deposit in the cooler part 
of the tube? (3) How would you explain its formation 
{knowing that illuminating gas contains hydrogen) ? (4) What 

is (a) the verbal and (b) the chemical equation for the reaction 
in A ? 

^Exercise 11 — Reaction between Sodium and Water — 
Teacher’s Exercise 

Materials. — Sodium, zinc sulfate solution, tea lead or wire 

gauze, litmus paper. 

Apparatus. — Test wire, test tube clamped over dish as in Fig. 23. 

Caution. — Sodium is a dangerous substance. It should 
be handled cautiously and used strictly according to direc¬ 
tions. Small fragments obtained for exercises should be 
protected from water by a mortar or dish. If any sodium 
is left from an exercise, it must not be thrown into the refuse 
jar, but returned to the bottle containing kerosene which 
protects the sodium. 

(a) With dry forceps remove a lump of sodium from the 
bottle, soak up the oil with filter paper, cut off three or four 
small pieces and put the lump back into the bottle; place a 
mortar over the pieces of sodium until needed. 

Fill an evaporating dish half full of water. Drop a piece of 
sodium upon the water in the dish, stand back and observe 
the result, waiting for the slight explosion before approaching 
the dish again. Repeat with the rest of the sodium, piece by 
piece. 

When the chemical action is over, stand the dish on a 
gauze-covered ring attached to an iron stand, and heat 
until the water is entirely evaporated. Meanwhile proceed 
with (6). 

When the water has evaporated, note the white residue. 
Test it in three ways. 


25 


(1) Moisten the end of a glass rod, touch the residue with 
it, and then draw this end across a piece of moistened red 
litmus paper. Observe the change in color of the litmus; 
this change is caused by hydroxides sodium hydroxide in 
this case. 

(2) Moisten the looped end of a clean test wire (Fig. 22), 
touch the residue with it, and hold the end of the wire in the 


■ ¥. / . / t -L . 


Fig. 22. — Test wires — platinum (upper), nichrome (lower) 


flame. Observe the color of the flame; it is caused by so¬ 
dium. The production of this color is a test for sodium. 

(3) Dissolve the rest of the residue in 10 cc. of water, pour a 
little of the solution into a test tube, add a few drops of zinc 
sulfate solution, and shake. Observe the, result. Now 
pour the rest of the solution into the test 
tube and shake well. Observe the result. 
These two results serve as a test for the 
hydroxide part of sodium hydroxide. 

(6) Cut off five or six pieces of sodium 
and protect them as in (a). 

Fill an evaporating dish two-thirds full of 
water. Fill a test tube full of water, cover 
and invert it, and clamp it as shown in 
Fig. 23. Make several holes in a piece of 
tea lead (about 5 cm. or 2 in. square), wrap 
Fl tus 3 foTstudying a sma ll piece of clean sodium loosely in the 
the reaction be- dry tea lead, and slip it under the test tube, 
tween water and (Wire gauze may be used instead of tea 
lead.) A gas will rise in the test tube. 
Proceed similarly with additional pieces of sodium and dry 
tea lead until the test tube is full of gas. Then unclamp 
it, keep it mouth downward, and hold a lighted match at 
the mouth. Observe the result immediately, especially at 
the mouth of the tube. 



26 

















Write in your laboratory notes answers to these questions. 
(1) What is the name of each substance formed in the reaction 
between water and sodium f (2) What is (a) the verbal and 
(6) the chemical equation for the reaction f 

Optional Exercises 

1. State the test for (a) sodium and ( b ) an hydroxide. 

2. Consult a textbook for the interpretation of the reac¬ 
tions in (a) (3), and write the equations. 


SUPPLEMENTARY EXERCISES ON HYDROGEN 

Supplementary Exercise 8 — Preparation of Hydrogen — 
Short Methods 

Materials. — Zinc, magnesium, aluminum, iron, dilute hydro¬ 
chloric acid, dilute sulfuric acid, sodium hydroxide. 

(a) Fill a test tube half full of dilute hydrochloric acid, 
stand it in the rack, and drop in a small piece of zinc. Hold 
a lighted match at the mouth of the test tube and observe 
the result. (If the test is not decisive, add more zinc, 
warm gently, or wait until more gas accumulates in the test 
tube.) 

Proceed in the same way with magnesium and iron (in the 
form of filings); use separate test tubes, and heat, if the 
action is slow. Observe the result in each case. 

( b ) Proceed as in (a), using dilute sulfuric acid. Observe 
the result in each case. 

(c) Roll two or three small, thin pieces of aluminum into 
a ball, drop it into a test tube, slip in a piece of sodium hydrox¬ 
ide about 2.5 cm. (or 1 in.) long, and add a little water. 
Warm gently. Test as in ( a ) and observe the result. 

Write in your laboratory notes answers to these questions. 

(1) What is the source of the hydrogen in each experiment? 

(2) What is the verbal equation for the chemical change in each 

case (except (c)) ? (3) What is the chemical equation for zinc 

and each acid ? 


27 




Supplementary Exercise 9 — The Reaction between Zinc 
and Sulfuric Acid — Teacher’s Exercise 

Materials. — Contents of the hydrogen generator from Exercise 9, 

sodium hydroxide and barium chloride solutions. 

Apparatus. — Evaporating dish, iron stand, etc. (Fig. 24). 

If the generator contains a solid (besides the zinc), add a 
little warm water to dissolve it. Then filter (see Appendix, 
§ 4 ) into an evaporating dish and concentrate the solution 
(1) by letting the dish remain undisturbed 
so that most of the water will evaporate 
or (2) by heating the dish on a gauze- 
covered ring which is attached to an iron 
stand as in Fig. 24. Heat until the volume 
of the liquid is reduced about one-half, 
and set the dish aside to cool. Crystals 
will separate from the solution. 

(a) Remove the crystals and dry with 
filter paper. Note the color, luster, and 
general shape. 

Wash some quickly in cold water, dis¬ 
solve the clean crystals in about 20 cc. of 
water, and divide the solution into two 
parts. 

(b) Test one part for a sulfate by adding barium chloride 
solution. Note the precipitate, especially the color and the 
fineness. It is barium sulfate, and is formed by the reaction 
between a sulfate and a dissolved barium compound. Its 
formation is a test for a sulfate. 

(c) Test the other part for zinc. (1) Add sodium hydrox¬ 
ide solution slowly with constant shaking until no more 
precipitate (zinc hydroxide) is formed, and note the color and 
texture; then (2) add considerable sodium hydroxide solu¬ 
tion, shake well, and note the final result. The precipitate 
of zinc hydroxide formed at first is changed by the excess of 
sodium hydroxide into soluble sodium zincate ; the behavior 
of zinc compounds with sodium hydroxide is a test for zinc. 

Write answers to these questions in your laboratory notes. 
(1) What substance besides hydrogen is formed by the reaction 

28 


d 


Fig. 24. — Apparatus 
for concentrating a 
solution 








between zinc and sulfuric cwidf (2) What is (a) the verbal 
equation and ( b ) the chemical equation for the reaction f 

Optional Exercises 

1. State in your own words the test for a sulfate. 

2. As in 1, for zinc. 

Supplementary Exercise 10 — Reduction of Copper Oxide by 
Hydrogen — Teacher’s Exercise 

Materials. — 5 gm. of copper oxide, 10 gm. of granulated zinc, 
dilute sulfuric acid, copper sulfate solution. 

Apparatus. —As in Fig. 25. The parts lettered A, B, C, D, E 
constitute the hydrogen generator used in Exercise 9. F is a 
large test tube fitted with a two-hole stopper; the delivery tube 
E passes through one hole and extends nearly to the bottom of the 
test tube. The right-angle tube G passes just through the other 
hole; the tube G is lengthened by the rubber tube H. 

Arrange the apparatus as in Fig. 25. Slip the copper 
oxide into the dry test tube F (Fig. 25), hold the tube in a 
horizontal position and 
tap it gently to spread 
the solid into a thin 
layer. Connect this 
test tube with the rest 
of the apparatus, and 
clamp it into the proper 
position, taking care 
not to crush the tube. 

Put the zinc into the 
bottle A. 

Pour about 2 cc. of _ _ 

copper Sulfate solution p IG 25. — Apparatus for reducing copper 
into the cup, fill the cup oxide by hydrogen 

nearly full with dilute 

sulfuric acid, pinch the clamp, and let about half the acid 
run into the generator bottle. If the hydrogen does not 
bubble freely, let more acid run in, taking care to keep a 
little acid in the cup. Add enough acid to keep the gas 

29 

























flowing steadily through the apparatus for at least two 
minutes before lighting the Bunsen burner. 

Heat gently the lower part of the test tube where the copper 
oxide is located.' Do not let the flame come near the rubber 
tube H. The gas must flow slowly through the apparatus 
during the heating; if it does not (as you can tell by the 
bubbles in the bottle or by smelling the gas at the end of the 
rubber exit tube), introduce more acid. If the test tube F 
should break, pinch the rubber tube D an instant to cut off 
the flow of hydrogen, and then extinguish the Bunsen burner 
flame. 

Continue to heat until a marked and permanent change is 
observed inside the test tube F. Then stop heating, and extin¬ 
guish the Bunsen burner flame at once. Note the two products 
in the test tube (disregarding any unchanged copper oxide). 

Write in your laboratory notes answers to these questions. 
(1) What is the name of each product in Ff (2) What com¬ 
pound was reduced by hydrogen t (3) What is (a) the verbal 
and (b) the chemical equation for the reaction in Ff 

Optional Exercises 

1. Describe briefly the whole experiment. 

2. Summarize in a few words how Supplementary Exer¬ 
cise 10 illustrates reduction. 

3. How does reduction differ from oxidation? 

4. If copper is heated in air and the solid product then 
heated in hydrogen, ( a ) what is oxidized, (6) what is 
reduced, (c) what oxidizes, and (d) what reduces ? 

WATER 

Exercise 12 — Purifying Water by Distillation 

Materials. — Copper sulfate and barium chloride solutions, 

ammonium hydroxide. 

Apparatus. — As in Fig. 26. A and B are large test tubes, and C 

is a 250 cc. bottle. 

Put about 15 cc. of water in the test tube A, add 2 or 3 cc. 
of copper sulfate solution (to color the water), and slip in 

30 


two short pieces of glass tubing (to prevent “ bumping ”). 
Arrange the apparatus as in Fig. 26; B is empty and C 
should be about three-fourths 
full of cold water. 

Heat the water in the test 
tube A to boiling. The steam 
passes into the test tube B 
and is condensed by the cold 
water in the bottle C. Con¬ 
tinue to heat until about 10 cc. 
has collected. Compare the 
color of the distillate in B 
with the copper sulfate solu¬ 
tion in A. 

Make two tests of the dis¬ 
tillate. 

(1) Test half of the distil¬ 
late for copper by adding 
ammonium hydroxide. If a 
copper compound is present, the solution will become deep 
blue. Note the result. 

(2) Test the rest of the distillate for a sulfate by adding 
barium chloride solution ; if a sulfate is present, a fine white 
precipitate of barium sulfate will be formed. Note the result. 

Write in your laboratory notes a brief description of the 
exercise and the result of each test of the distillate. 

*Exercise 13 — Suspension and Solution of Solids in Water 

Materials. — Fine clay, calcium sulfate, sodium chloride, potas¬ 
sium permanganate, sodium hydroxide (solid), chalk (powder). 

Put about 1 gm. of the powdered substances in separate 
test tubes (use only a few crystals of potassium perman¬ 
ganate), add 10 cc. of water, and shake well. Note the 
evidence of suspension or solution. In case of doubt, shake 
again. If there is still some solid, let it settle, filter half of 
the clear liquid into an evaporating dish and evaporate the 

31 



Fig. 26. — Apparatus for distilling 
water 












filtrate by heating the dish on a gauze. Note any definite 
and conspicuous evidence of solubility. 

Copy the table, given below, in your laboratory notes and 
insert each result, using the terms suspension and solution. 


Solution and Suspension of Solids in Water 


Solvent — 10 cc. 

Solid — 1 gm . 

Result 


1. Clay 

1. 


2. Calcium Sulfate 

2. 

Water at temperature 

3. Sodium Chloride 

3. 

of Laboratory 

4. Potas. Permanganate 

4. 


5. Sodium Hydroxide 

5. 


6. Chalk 

6. 


^Exercise 14 — Effect of Heat on the Solubility of 
Solids in Water 

Materials. — About 5 gm. each of powdered copper sulfate and 

potassium chlorate, calcium hydroxide solution for (c). 

(a) Label two test tubes, I, II. Put 10 cc. of water into 
each. To I add 1 gm. of powdered copper sulfate, and to II 
add 1 gm. of powdered potassium chlorate. Shake each test 
tube, and then allow them to stand undisturbed until the 
solid settles. Note the evidence of solubility in each case. 
(Save for (6).) 

(b) Heat I, and add gradually 2 gm. of powdered copper 
sulfate. Note whether it all dissolves. Heat II and add 
2 gm. of powdered potassium chlorate. Note whether it all 
dissolves. Add the rest of each solid to the respective tubes, 
and heat (but do not boil). Note the effect of increased heat 
on the solubility of the solid. Save for Exercise 15. 

(c) Fill a test tube half full of clear calcium hydroxide 
solution, and heat it to boiling. Observe the result. Com¬ 
pare with the cold solution. Note the effect of increased 
heat on the solubility of calcium hydroxide. Note how the 
result differs from (6). 

Write a brief account of this exercise in your laboratory notes. 

32 









Exercise 15 — Formation of Crystals 


Materials. — Solutions from Exercise 14, thread or string. 
Apparatus. — 2 evaporating dishes or small beakers. 


If the contents of the test tubes is not liquid, add a little 
water, heat gently until the solid dissolves, and pour the hot 
solution into separate dishes (or beakers). 

Suspend a piece of thread or string in each 
solution, and let the solute crystallize (Fig. 27). 

Remove the thread when crystals have formed 
on it. Examine a well-shaped crystal. 

Write a brief account of this exercise in Fig 27 _ Crys _ 
your laboratory notes. tailizing 



^Exercise 16 — Effect of Shape on the Solubility of a Solid — 
Teacher's Exercise 

Material. — Crystallized alum. 

Apparatus. — 2 large test tubes fitted with corks. 

Weigh about 2 gm. of crystallized alum (in one lump, if 
possible) on the scales, and counterpoise it with a second 
quantity of equal weight. Pulverize the latter in a mortar. 
Put each in a test tube, add 25 cc. of water, and insert the 
cork. Note the time. Shake the tubes gently until the 
powder has dissolved. Note the time again. Estimate 
the amount of alum left in the other tube, or, if time permits, 
continue to shake it at intervals until the solid has dissolved, 
and note the time again. 

Compare the time required to dissolve the powder and the 
crystal. 

Write a brief account of this exercise in your laboratory notes. 


^Exercise 17 — Testing Crystals for Water of Hydration 

Materials. — Sodium carbonate, potassium dichromate, ferrous 
sulfate, borax, barium chloride, zinc sulfate, sodium sulfate, 
calcium sulfate, sodium chloride, potassium nitrate, sugar, 
magnesium sulfate, potassium bromide. 

Test several of the substances for water of hydration by 
heating gently a dry specimen in a dry test tube inclined so 

33 






that the open end is the lower. Observe in each case the 
change in appearance of the solid during the heating, relative 
amount of water liberated (if appreciable), and appearance 
of the residue. 

Write an account of this exercise in tabular form in your 
laboratory notes. 

^Exercise 18 — Per Cent of Water of Hydration in a 
Crystallized Compound 

Material. — Crystallized copper sulfate (powdered) for A and 
crystallized barium chloride for B. 

Apparatus. — Scales and evaporating dish for A, balance and 
covered porcelain crucible for B. (Fig. 28.) 

Object. — To find the weight of water lost by heating a 
weighed amount of crystallized copper sulfate, and to cal¬ 
culate the per cent of water of hydration. 

A. First Method. Copy the form of Record, as given 
below, in the notebook, and enter all weights as soon as the 
weighing is completed. 

Clean and dry an evaporating dish and weigh it to a deci¬ 
gram on the scales. Put about 10 gm. of powdered copper 
sulfate in the dish and weigh to a decigram. Enter the 
weight at once. 

Record 

Weight of dish and copper sulfate before 


heating. gm. 

Weight of dish. gm. 

(а) Weight of copper sulfate. gm. 

Weight of dish and contents before heating . gm. 

Weight of dish and contents after heating . gm. 

(б) Weight of water of hydration . . . gm. 

Per cent of water of hydration . . . per cent 


Stand the dish with its contents on a gauze-covered ring 
attached to an iron stand, heat gently for five or ten minutes, 
and then intensely until the substance becomes a gray powder. 

34 







Do not touch the substance, and take special pains not to 
lose any. Cool slowly and weigh as before. Enter the 
weight at once. 

Complete the entries in the Record. Calculate the per 
cent of water of hydration (i.e. divide ( b ) by (a)). Submit 
the result to the Teacher before throwing 
away the contents of the dish. 

B. Second Method. Prepare a form of 
Record similar to that in A, and enter the 
weighings as soon as made. 

Weigh accurately on the balance a clean, 
dry porcelain crucible. Put about 2 gm. of 
crystallized barium chloride in the crucible, 
and weigh accurately. Support the cruci¬ 
ble on a triangle as in Fig. 28, and put on 
the cover. Heat gently at first, and then 
strongly for about fifteen minutes. Let the 
crucible cool, and then weigh it (uncovered). 

Calculate the per cent of water of hydra¬ 
tion. Submit the result to the Teacher 
before throwing away the contents of the 
crucible. 

Optional Exercises 

1. Compare your result with (1) the correct per cent and 
(2) the class average. 

2. Suggest a source of error in this exercise and how it can 
be corrected. 

Exercise 19 — Electrolysis of Water (Acid Solution) — 
Teacher’s Exercise 

Materials. — Sulfuric acid, joss stick, taper. 

Apparatus. — Hofmann apparatus, source of electric current. 

Fill the Hofmann apparatus (Fig. 29) with water contain¬ 
ing 10 per cent of sulfuric acid. The water in the reservoir 
tube should stand a short distance above the tip of the gas 
tubes after the stopcock in each has been closed. (Water 

35 



Fig. 28. — Covered 
crucible arranged 
for finding the 
water of hydration 
in a crystallized 
compound 









does not conduct electricity. The acid makes a conducting 
solution. At the end of the exercise the solution contains the 
same amount of acid as at the beginning.) 

Connect the platinum terminal wires with a battery of at 


least three cells 



Fig. 29. — Hofmann 
apparatus for elec¬ 
trolysis 


cock again, let 


(or a direct current reduced by suitable 
resistance). As the action proceeds, small 
bubbles of gas rise and collect at the top 
of each tube. Allow the current to run 
until the smaller volume of gas is 8 to 
10 cc. 

Measure the height of each gas column. 
Assuming that the tubes have the same 
diameter, the volumes are in approximately 
the same ratio as their heights. Note how 
the volumes compare. 

Test the gas as follows: (a) Open the 
stopcock of the tube containing the smaller 
quantity of gas long enough to allow the 
water (or air) to run out of the glass tip, 
and then close it immediately. Light the 
joss stick and make the end glow. Then 
let out a little gas upon a glowing joss 
stick, and observe the result. Close the 
stopcock as soon as the result is observed. 
Repeat, if gas is available. 

( b ) Open the other stopcock long enough 
to force out the water (or air) in the glass 
tip and then close it. Open the stop- 
out a little gas slowly, hold a lighted 


match for an instant at the end of the tip, and im¬ 
mediately thrust a taper into the small and almost color¬ 
less flame. Watch for a change in the taper. Close the 
stopcock as soon as the change is seen. Repeat, if gas is 
available. 


Write in your laboratory notes answers to these questions. 
(1) What gas was found in (a) and in ( b ) f (2) Which gas 
has (a) the larger and ( b) the smaller volume f (3) How do 
the volumes compare f 


36 











Optional Exercises 

1. Describe this exercise. 

2. What does this exercise show about the composition 
of water? 

3. What does this exercise show about the relation between 
electrical and chemical energy? 

SUPPLEMENTARY EXERCISES ON WATER 

Supplementary Exercise 11 — Preparation and Properties of 
Distilled Water — Teacher’s Exercise 

Materials. — Water containing a little of three impurities 
dirt, calcium chloride, and sodium sulfate; potassium per¬ 
manganate, silver nitrate, barium chloride, and ammonium oxalate 
solutions. 

Apparatus. — Liebig condenser, etc., as in Fig. 30. 

I. Preparation. — Fill the flask A half full of the water 
containing the three impurities mentioned above, add a few 
short pieces of glass tubing to insure even boiling, and con¬ 
nect with the condenser at B as shown in Fig. 30. Attach 



Fig. 30. — Liebig condenser arranged to distil water 


the inlet (lower) tube C to the faucet, fill the condenser slowly, 
and regulate the current so that a small stream flows contin¬ 
uously from the outlet tube D into the sink or waste pipe. 

Heat the liquid in A to boiling. The steam will condense 
as it passes through the inner tube, and drop off as the dis- 

37 


















tillate, into the receiver E. Reject the first 5 or 10 cc. of the 
distillate; they may contain impurities. As the distillate 
collects in the clean receiver E, proceed with the tests as in II. 

II. Properties. — (a) While the distillate is collecting, 
test the impure water for organic matter. Put 10 cc. of the 
impure water in a test tube, add a few drops of concentrated 
sulfuric acid, and enough potassium permanganate solution 
to color the mixture a light reddish purple. Mix well by 
stirring with a glass rod. Grasp the test tube with the test 
tube holder and heat gently until the liquid begins to boil, 
taking care to remove the test tube from the flame occasionally 
to prevent the liquid from spurting out. If organic matter 
is present, the color of the solution will be changed to brown. 

Test in the same way 10 cc. of the distilled water, taking 
care to use a very clean test tube. Compare the results. 

( b ) Test separate portions (about 10 cc.) of the impure 
water for different kinds of mineral matter. In a similar way 
test the distilled water and compare the corresponding tests. 

(1) Chlorides. — Add a few drops of silver nitrate solution, 
and note the result. The white, curdy solid is silver chloride, 
which is formed by the reaction between silver nitrate and the 
dissolved chloride. All soluble chlorides produce the same 
result. (Precaution. — In testing for a chloride it is best 
to add also some nitric acid to dissolve substances which 
might be mistaken for silver chloride.) 

(2) Sulfates. — Add a few drops of barium chloride solu¬ 
tion, and note the result. The white, fine precipitate is 
barium sulfate, which is formed by the chemical action 
between barium chloride and the dissolved sulfate; its 
formation is a test for any sulfate in solution. 

(3) Calcium (or lime) compounds. — Add a few drops of 
ammonium oxalate solution, and note the result. The white 
precipitate is calcium oxalate. Its formation serves as a test 
for dissolved calcium compounds. 

Write a brief description of this exercise in your laboratory 
notes. 

Write also the test for (1) a chloride , (2) a sulfate , and (3) a 
calcium compound. 


38 


Optional Exercises 

1. Test different samples of water for impurities, as in 

(а) and (6). 

2. Taste of distilled water. Compare with ordinary drink¬ 
ing water. Why does distilled water have such a flat taste ? 

Supplementary Exercise 12 — Purification of Water — 
Teacher’s Exercise 

Materials. — Water (100 cc.) rendered turbid with fine clay; 
cotton, sand, powdered charcoal, alum solution, ammonium 
hydroxide. For ( d ) bad-smelling water, chlorine water. 
Apparatus. — Two funnels, test tube fitted with a cork (for (d)). 

(а) Put a loose plug of cotton in the apex of a funnel, 
fill the funnel one-fourth full of sand, pour 25 cc. of the turbid 
water on the sand, and catch the filtrate in a test tube. 
(Meanwhile do ( b ), etc.) Note the result. Compare the 
filtrate with the sample. 

(б) Proceed as in (a), using powdered charcoal instead of 
sand. Note the result. Compare the filtrates from (a) and 

(б) with the sample. 

(c) Fill a large test tube about four-fifths full of the 
turbid water. Add about 5 cc. of alum solution and mix 
well. Then add about 10 cc. of ammonium hydroxide, and 
mix well again. Let the mixture stand undisturbed sev¬ 
eral minutes. Note the result. Compare the upper liquid 
(1) with the sample and (2) with the filtrates from (a) and ( b ). 

(d) Add 2 cc. of chlorine water to a test tube nearly full of 
bad-smelling water, cork, shake well. Note the result. 
Compare with the sample. 

Write a brief account of this exercise in your laboratory notes. 

Supplementary Exercise 13 — Anhydrous Compounds 

Materials. — Hydrated (crystallized) copper sulfate. 

(a) Pulverize a little hydrated copper sulfate and note the 
color. Put it in a test tube, hold the tube horizontal, and 
spread the powder along the tube. Hold the mouth of the 

39 


tube slightly lower than the other end, and heat gently. 
Begin to heat at the closed end and move the tube in the flame 
so that all the liberated water is finally driven from the tube. 
Note the color of the anhydrous solid. Let the tube cool. 

(i b ) When the tube is cool, cautiously add a little water, 
and let it run down upon the solid. Note the effect of the 
water on the color of the solid. 

Write a brief account of this exercise in your laboratory notes. 
Write answers to these questions in your laboratory notes. 
(1) What is the difference between a hydrated and an anhydrous 
compound? (2) What is the color of hydrated copper sulfate? 
Dehydrated ? A nhydrous ? 

Supplementary Exercise 14 — Efflorescence — Teacher’s 
Exercise 

Materials. — Sodium carbonate, sodium sulfate, ferrous sulfate, 
potassium ferrocyanide, barium chloride, magnesium sulfate. 

Put a fresh, or a recently broken, crystal of several of the 
substances on a piece of filter paper, and label each. Let 
them remain exposed to the air for an hour or more. Note 
any marked change in the appearance. 

Write an account of this exercise in tabular form in your 
laboratory notes. 

Write also answers to these questions. (1) What does the 
change, if any, show about the air? About the crystal? (2) To 
what is the change due ? 

Supplementary Exercise 15 — Efflorescence and 
Deliquescence — Teacher’s Exercise 

Materials. — Crystallized copper sulfate, concentrated sulfuric 
acid, sodium hydroxide. 

Apparatus. — 4 test tubes fitted with corks, thread, copper or iron 
wire. 

A. Select two pieces of crystallized copper sulfate which 
will just slip into a test tube. Tie a thread around each 
piece. Put 10 cc. of water into one test tube, and 10 cc. of 

40 


concentrated sulfuric acid into the other, taking care not to 
leave any drops on the inside of the test tube, and insert the 
cork tightly (Fig. 31); smear a little vase¬ 
line around the upper edge of the test tube 
containing the acid to make the joint air 
tight. 

Let the test tubes stand in the rack undis¬ 
turbed for several hours (or until the next 
laboratory period), and then examine each 
solid. Compare them with each other and 
with a sample of the original substance. 

Note the change, if any, in each case; note 
also the degree of change. 

B. Proceed as in A, using sodium hy¬ 
droxide. Wind the wire around the solid and attach the 
wire to the thread. Observe, as in A. 


Fig. 31.—Appara¬ 
tus for showing 
efflorescence and 
deliquescence 


Write a brief account of this exercise in your laboratory notes. 
Write also answers to these questions. (1) How do A and B 
differ? (2) How can solids be kept (a) dry , (6) hydrated, 
( c ) wet, ( d ) anhydrous? 


Supplementary Exercise 16 — Supersaturated Solution — 
Teacher’s Exercise 

Material. — Sodium thiosulfate. 

Apparatus. — Test tube fitted with a cork. 

Fill a test tube half full of crystallized sodium thiosulfate 
and add 2 or 3 cc. of water. Warm slowly until all the solid 
has dissolved. Pour the solution into a warm, clean, dry 
test tube, insert a cork, and let it stand undisturbed until 
cool. Note the change in the solution, if any. Drop in a 
small crystal of sodium thiosulfate and watch for a definite 
change. Note what happens. Observe the final result. 

Write a brief account of this exercise in your laboratory notes. 
Write also answers to these questions. (1) What is the 
difference between a saturated and an unsaturated solution ? 
(2) How could you determine whether a cold solution is satu¬ 
rated, unsaturated, or supersaturated? 

41 




Supplementary Exercise 17 — Qualitative Composition of 
Water — Teacher’s Exercise 


Materials. — Chlorine water (see Supp. Exer. 19), joss stick. 
Apparatus. — As in Fig. 32. The tube is about 1 m. long and 
closed at one end. 




Fill the tube with chlorine water, cover the open end with 
the thumb or finger, invert the tube, and immerse the open 
end in a mortar or an evaporating dish, 
which should be nearly full of chlorine water 
(Fig. 32). Clamp the tube in an upright 
position, and stand the whole apparatus 
where it will receive the direct sunlight for 
several hours. Bubbles of gas will collect 
at the top. 

When sufficient gas for a test has collected, 
unclamp the tube, cover the open end with 
the thumb or finger, invert, and put a glow¬ 
ing joss stick into the gas. Repeat as long 
as any of the gas remains. Note the result. 

Write answers to these questions in your 
laboratory notes. (1) What gas is produced 
by the interaction of chlorine and water f 
(2) What evidence about the composition of 
Fig. 32. — Appa- water is given by (a) interaction of water and 
ratus for show- sodium and (b) reduction of copper oxide by 
is g aConstituent hydrogen (or carbon) f (3) Of what two ele- 
of water ments is water composed ? 



EQUIVALENT WEIGHTS — FORMULA 
Exercise 20 — Equivalent Weight of Zinc 

Materials. — Zinc, dilute sulfuric acid. 

Apparatus. — As in Fig. 33, pneumatic trough (not zinc), ther¬ 
mometer, barometer. 

Object. — To find the number of grams of zinc chemically 
equivalent to 1 gram of hydrogen. 

42 











Copy the form of Record (given below) in your labora¬ 
tory notes and enter each item as soon as the weighing, 
measuring, or reading 
is made. 0 

Construct and ar¬ 
range the apparatus 
(Fig. 33) to collect a 
gas over water, and 
have it inspected by 
the Teacher. 

Obtain a piece of 
weighed zinc from the 
Teacher, or weigh 
from 0.45 to 0.5 gm. 
of zinc on the bal¬ 
ance. Take a single 
piece and weigh it exactly 



Fig. 33. — Apparatus for finding the equivalent 
weight of zinc 


Enter in the Record as Zn. 


Record 

Weight of zinc taken (Zn) . gm 

Observed volume of hydrogen (V') . cc 

Temperature (t) ° 

Pressure ( P') . mm 

Vapor pressure (a) . mm 

Corrected volume of hydrogen (F). cc 

Weight of corrected volume of hydrogen (W) . . gm 

Equivalent weight of zinc ( E ). gm 


Put the weighed zinc into the bottle A. Fill the bottle 
with water and insert the stopper with all its tubes. Next 
fill the remainder of the apparatus with water by filling the 
cup with water and then admitting it repeatedly until all 
air is forced out of the bottle and tubes; take care never to 
let the water in B fall below the lower opening of the cup. 
Note that the inner end of the tube C does not extend below 
the stopper — important. 

Fill a 250 cc. bottle with water and invert it upon the 
support in the trough (a zinc trough must not be used). 
Put the end of the delivery tube under the support and ask 

43 























for a final inspection. Heat about 50 cc. of dilute sulfuric 
acid in a test tube. Fill the cup and introduce the hot acid 
(Care!) in separate portions slowly into the bottle A, taking 
the same precaution as before. The liberated hydrogen 
will slowly accumulate in the receiving bottle. (Note. — 
While the hydrogen is being evolved, Exercise 21 may be 
done.) 

Let the action continue until the zinc is used up ; disregard 
a minute speck or two which may be left from the zinc. 
Then force over into the collecting bottle all gas in the 
apparatus by admitting water carefully as before. Lay a 
piece of dry filter paper upon the bottom of the bottle, grasp 
the bottle firmly, carefully joggle it to dislodge any gas 
bubbles which may be underneath the support, slide the 
bottle from the support, and lower it into the water until 
the water is at the same level inside and outside the bottle; 
then slip two pieces of filter paper beneath the bottle, cover 
the mouth firmly, lift the bottle from the trough and stand it, 
right side up, upon the desk. Stand a thermometer in the 
bottle, and after a few minutes read the thermometer while 
the bulb is in the water; enter as t. 

Fill a 250 cc. graduate exactly to the mark with water, 
remove the thermometer from the bottle, and very carefully 
fill the bottle with water from the graduate; read and enter 
(as V') the exact volume of water added ; this is numerically 
the same as the volume of hydrogen liberated. Read the 
barometer, and enter as P'. Find the vapor pressure corre¬ 
sponding to the observed temperature (see Appendix, § 1), 
and enter as a. 

Correct the observed volume ( V') of hydrogen for tempera¬ 
ture, pressure, and vapor pressure, and enter as V. 

Since 1000 cc. of dry hydrogen weigh 0.09 gm., the weight 
(W) of the corrected volume of hydrogen (F) is found by 
the proportion 

1000: V :: 0.09 : W. 

And the weight of zinc equivalent (E) to 1 gram of hydrogen 
is found by W : Zn :: 1: E. Enter this weight (the equivalent 
weight) of zinc as E. 


44 


Submit the result to the Teacher before taking the appa¬ 
ratus apart. 

Write a brief account of this exercise in your laboratory notes. 

Optional Exercises 

1. Calculate the atomic weight of zinc by multiplying the 
equivalent weight (found in this exercise) by 2. 

2. Compare this calculated atomic weight with the approx¬ 
imate atomic weight. 

3. Calculate, as in 1, from the class average. 

4. Compare the number obtained in 3, as in 2. 

^Exercise 21 — Equivalent Weight of Magnesium 

Materials. — Magnesium ribbon, concentrated hydrochloric acid. 
Apparatus. — A 100 cc. tube, pneumatic trough (not zinc), ther¬ 
mometer, barometer, tall jar ( e.g . 1000 cc. graduate). 

Object. — To find the number of grams of magnesium 

equivalent to 1 gm. of hydrogen. 

Copy in your laboratory notes the form of Record as in 
Exercise 20, and enter the items, when available, in the 
proper place. 

Obtain a piece of weighed magnesium from the Teacher or 
weigh accurately from 0.06 and 0.07 gm. of magnesium ribbon, 
preferably in a single piece. Enter the exact weight as Mg. 
Have the trough (not zinc) half full of water. 

Pour 8 cc. of concentrated hydrochloric acid into the 100 
cc. tube and fill the tube completely with cold water. Put 
the magnesium into the water in the tube, cover the end of 
the tube with the thumb or finger, invert, and stand it in the 
trough, but keep the end loosely closed to prevent the mag¬ 
nesium from slipping out. As the acid sinks through the 
water and reaches the magnesium, action begins vigorously. 
Hydrogen rises rapidly in the tube and usually carries the 
magnesium with it. Watch the operation, and shake the tube 
to prevent the magnesium from sticking to the inside. If 
a piece of magnesium should stick to the inside of the tube, 
close the end of the tube tightly with the finger, lift it from 

45 


the water, incline it enough to let the liquid run down and 
loosen the magnesium, then quickly put the end of the tube 
beneath the water, and remove the finger. 

When all the magnesium has disappeared, close the end .of 
the tube, remove (Care!) the tube to a tall jar of water, and 
let it stand five or more minutes ; then, by a clamp (without 
touching the tube with the hands), adjust the height so that 
the water levels are the same inside and outside of the tube. 
Read the volume of hydrogen, and enter as the observed 
volume (V'). Read the barometer and the thermometer 
(keeping the bulb in the water). Enter as P and t. 

Correct the observed volume (7') for temperature, pres¬ 
sure, and vapor pressure, and enter as the corrected volume 
(7). Find the weight (17) of this volume (7) of hydrogen 
as in Exercise 20. Calculate the weight of magnesium 
equivalent to 1 gm. of hydrogen, as in Exercise 20. Enter 
this weight as E. 

Submit the result to the Teacher before letting out the gas. 


Write a brief account of this exercise in your laboratory 
notes. 

Optional Exercises 

As in Exercise 20. 


Exercise 22 — Formation of the Compound Copper Sulfide 

Materials. — Fine copper wire (about 2 m. (6 ft.)), powdered 
sulfur. 

Apparatus. — Porcelain crucible and cover, crucible block, triangle, 
balance and weights. 

Object. — To find the weight of sulfur that combines 
with a certain weight of copper, and calculate the weight 
of sulfur that would combine with 1 gram-atomic-weight 
of copper (i.e. with 63.57 gm.). 

Copy the form of Record, as given below, in your labora¬ 
tory notes. When you weigh, take the notebook to the 
balance and enter all weights in the Record as soon as the 
weighing is made. In weighing ask directions or follow 
Appendix, § 8. 


46 



Q 


Fig. 34. — Crucible block 


Clean and dry a porcelain crucible and cover. Carry it 
to the balance in the crucible block (Fig. 34). Weigh the 
uncovered crucible accurately on the 
balance. Coil the piece of copper 
wire into a flat spiral, put it in the 
crucible, and weigh both. 

Put the crucible on the crucible 
block, and carry it, together with 
the cover, iron stand, ring, triangle, and burner, to the hood. 
Fill the crucible half full of powdered sulfur, stand it on the 
triangle (Fig. 35), put on the cover, and 
heat gently to melt the sulfur. Remove 
the cover, and if the copper wire is not 
completely covered with sulfur, add more 
sulfur. Put on the cover, and heat the 
crucible as long as the blue flame of burn¬ 
ing sulfur is seen between the crucible 
and cover. Continue to heat two or three 
minutes more, especially the upper part 
of the crucible. Then take off the cover, 
and if any unburned sulfur is seen, heat 
until all the sulfur is gone. 

Let the crucible cool. Carry it to the 
balance as before, and weigh (without 
cover). Complete the Record. 

Calculations. (1) Find the weight of sulfur that would 
combine with 63.57 gm. of copper by this proportion : 

Wt. of Copper: Wt. of Sulfur:: 63.57 : X., X = gm. of sulfur. 

(2) Find the per cent of copper and of sulfur in the product 
(copper sulfide) thus : — 


Fig. 35. — Covered 
crucible on triangle 


% of copper = 
% of sulfur = 


Wt. of copper 
Wt. of copper sulfide 
Wt. of sulfur 


X 100 


X 100 = 


Wt. of copper sulfide 
(3) Find the formula of copper sulfide thus: Divide 
the per cent of each element by the corresponding atomic 
weight, and reduce the quotients to the smallest whole 
numbers. These numbers are the subscripts of the corre- 

47 













sponding elements in the formula. (Note. — Unless the 
exercise is done accurately, the correct formula is not readily 
calculated from the per cents found.) 

Record 

Grams 

Wt. of crucible and copper. 

Wt. of crucible.. 

Wt. of copper. 

Wt. of crucible and contents after heating .... 

Wt. of crucible.. 

Wt. of copper sulfide . 

Wt. of copper.. 

Wt. of sulfur. 

Write in your laboratory notes the results of ( 1 ), (#), (3). 

SUPPLEMENTARY EXERCISE ON EQUIVALENT 
WEIGHTS 

Supplementary Exercise 18 — Equivalent Weight of 
Aluminum 

Proceed as in Exercise 20. .Use about 0.17 gm. of alumi¬ 
num (taking care to weigh exactly the amount used). Use 
hot concentrated hydrochloric acid instead of dilute sulfuric 
acid. Record and calculate as in Exercise 20. 

Optional Exercises 

As in Exercise 20. (In 1 the multiplier is 3.) 

CHLORINE AND HYDROCHLORIC ACID 

^Exercise 23 — Preparation and Properties of Chlorine 

Materials. — Concentrated hydrochloric acid, potassium per¬ 
manganate, wax taper, iron thread, copper wire (15 cm. long), 
colored cloth, piece of newspaper, litmus paper, cotton, turpen¬ 
tine. (Note. — pleaching powder (10 gm.) and concentrated sul¬ 
furic acid (10 cc.) — Care —may be used in place of potassium 
permanganate and hydrochloric acid.) 

Caution. — Do this exercise in the hood. 

48 













I. Preparation. — Warm four dry bottles, cover the 
bottom of each with a thin layer of crystallized potassium 
permanganate, add 5 cc. of concentrated hydrochloric acid 
to each (see Note above), and cover with a piece of filter 
paper pressed down to form a loose cap. Chlorine will 
slowly fill the bottles. When the (greenish) color shows 
that a bottle is full of the gas, proceed at once with it as 
in II (a). Use the other bottles when full. 

II. Properties. — (a) Remove the paper from a bottle of 
chlorine and thrust a blazing wax taper into the gas. Observe 
the result at once, e.g. effect on the gas and 
the taper, and formation of smoke. 

(b) Using the same bottle as in (a), hold 
a lighted wax taper just inside the bottle. 

Move it up and down slowly. If it goes out, 
relight it, and continue. (If a taper is un¬ 
satisfactory, use a candle attached to a wire.) 

Observe the result, especially the formation 
of white and of black smoke. 

(c) Twist one end of a copper wire around 

a wad of iron thread (Fig. 36), heat the edge 
of the wad for an instant in the flame, and 
quickly lower it into another bottle of chlorine. _ ^ 

Observe the result, especially the evidence of G f cotton and 
chemical action. iron thread for 

(i d ) Into the third bottle of chlorine hang properties 1 of 
(by a wire) pieces of colored cloth, litmus chlorine 
paper (both colors), newspaper, and paper 
containing writing in lead pencil, ink (black and red) — all 
moistened with water; cork or cover the bottle. Let the 
whole remain undisturbed for a few minutes (e.g. while ( e ) 
is being done). Then note what is bleached and what 
is not. 

(e) Twist one end of the copper wire around a wad of 
cotton, saturate the cotton with turpentine, and lower the 
cotton into a bottle of chlorine. Observe at once the forma¬ 
tion of white smoke and then the conspicuous result. (This 
experiment works well if the turpentine is warm (Care!) 
and the bottle is full of chlorine.) 

49 






Note. — As soon as II (e) has been completed, fill each 
bottle with water (in the hood) and pour the contents at 
once into a waste jar in the hood. 

Write in your laboratory notes answers to these questions. 
(1) What is the color of chlorine f Is this gas heavier or lighter 
than airf Does it bumf Does it support ordinary com¬ 
bustion f (2) Knowing that wax and turpentine consist of 
compounds of carbon and hydrogen, how do you explain the 
observations in (b) and (e)f (3) What was bleached and 
not bleached in (d) f (4) What compound was formed in (c) f 

^Exercise 24 — Preparation and Properties of Hydrogen 
Chloride and Hydrochloric Acid 

Materials. — Sodium chloride, concentrated sulfuric acid, litmus 
paper (blue), ammonium hydroxide. 

Apparatus. —As in Fig. 37 (or Fig. 38). A is a 250 cc. Erlen- 
meyer flask which stands on a gauze-covered ring; the parts 
lettered B, C, D, E have been used 
in preceding experiments. F is a 
piece of stiff paper. 

Note. — Perform this experiment 
in the hood. 

I. Preparation. — (1) Hydrogen 
chloride. — Put 8 cc. of water into 
a small bottle or an evaporating 
dish, cautiously add 10 cc. of con¬ 
centrated sulfuric acid, and stir 
until the two are mixed. While 
this mixture is cooling, weigh 10 gm. 
of sodium chloride, slip it into the 
flask, and arrange the apparatus as 
shown in Fig. 37. If a straight 
thistle tube is used (Fig. 38), the 
lower end must be below the surface 
of the acid. 

Pour half of the cold acid through the funnel into the flask, 
let it settle through the sodium chloride, and then add the 
remaining acid. Heat the flask gently. Hydrogen chloride 

50 



Fia. 37. — Apparatus for pre¬ 
paring hydrogen chloride 
and hydrochloric acid 














passes into the bottle G, which should be removed when full. 
(A piece of moist blue litmus paper held near the mouth of 
the bottle will show when it is full. Let the gas enter a 
minute or so after the first test.) Collect three bottles of the 
gas, cover each tightly, when filled, with a piece of dry filter 
paper, and set aside for II. 

(2) Hydrochloric acid. — As soon as the third bottle of 
gas has been collected, put in its place a bottle one-fourth 
full of water. Adjust the delivery tube E so that the lower 
end is a short distance above the 
surface of the water. Continue to 
heat the flask at intervals, and the 
gas will be absorbed by the water. 

Shake the bottle occasionally. Mean¬ 
while perform II. 

U. Properties of hydrogen chlo¬ 
ride. — (a) Insert a blazing joss stick 
once or twice into a bottle of the 
gas, and observe the effect on both 
joss stick and gas. 

(6) Using the bottle from (a), 
hold a piece of wet filter paper 
near the mouth (or drop it inside). 

Observe the result. 

(c) Invert a bottle of the gas, and stand it in a vessel of 
water ( e.g . the pneumatic trough). Shake the bottle vigor¬ 
ously up and down, still keeping its mouth under the water. 
Observe the change inside the bottle. Cover the mouth of 
the bottle with the hand, invert, and stand it on the desk. 
Test the contents (1) with blue litmus paper and (2) by 
adding a few drops of silver nitrate solution. Note each 
result. 

(i d ) Drop into the remaining bottle of gas a piece of filter 
paper wet with ammonium hydroxide. Note the result. 

III. Properties of hydrochloric acid. — Remove the bottle 
in which the hydrogen chloride is being absorbed. This 
liquid is dilute hydrochloric acid. 

Determine its general properties, e.g. taste (cautiously), 
action with litmus, with magnesium (using 10 cc. of the hydro- 

51 



Fig. 38. — Simple apparatus 
for hydrogen chloride and 
hydrochloric acid 




















chloric acid), and with silver nitrate solution. Note the 

result in each case. ., ' 

Note. — As soon as II ( b ) has been performed, add water 
to the flask or test tube, shake well, and pour the contents 
into a waste jar in the hood. 

Write a brief description of I in your laboratory notes. 

Write answers to these questions in your laboratory notes. 
(1) What is ( a ) the verbal and (b) the chemical equation for the 
reaction in I? (2) Does hydrogen chloride (a) burn or (6) 
support combustion? (3) What is the explanation of the 
result in II (b)? (4) What property of hydrogen chloride is 

shown by the first part of II (c)? (5) What are the chemical 

equations for the reactions in II (c) (2) and (d) ? 

Optional Exercises 

1. Summarize the properties of hydrochloric acid. 

2. Enumerate several physical properties of hydrogen 
chloride. 

^Exercise 25 — Tests for Hydrogen Chloride, Hydrochloric 
Acid, and Chlorides 

(а) Recall a specific property which would serve as a test 
for hydrogen chloride. 

(б) As in (a) for hydrochloric acid. 

(c) Apply the silver nitrate test for a chloride by adding 
a few drops of this reagent to a few cubic centimeters of a 
solution of several chlorides in separate test tubes (e.g. 
ammonium chloride, ferric chloride, and calcium chloride). 
Note each result. 

Note. — It is desirable, though not always necessary, to 
add nitric acid to dissolve certain compounds (e.g. silver 
carbonate) which might be formed in testing with silver 
nitrate. 

Write in your laboratory notes a brief, accurate statement of 
the test for hydrochloric acid and soluble chlorides. 

Write also the equation for the reaction. 

52 


^Exercise 26 — Insoluble Chlorides 

Materials. — Silver, lead, and mercurous nitrate solutions. 

(a) Put about 5 cc. of silver nitrate, lead nitrate, and mer¬ 
curous nitrate in separate test tubes, and label each tube. 
Add 5 cc. of dilute hydrochloric acid to each solution, shake, 
and note the result. Note the color of each precipitate. 
Decide on a name for each. 

(b) Shake well, and pour about half of each precipitate into 
separate test tubes. Save the rest of the precipitates for (c). 

Fill each of the three test tubes half full of water, and heat 
to boiling. Note which chloride dissolves in hot water. 

(c) Fill each of the test tubes saved in ( b ) nearly full with 
ammonium hydroxide. Shake well. Warm gently. Note 
the effect of ammonium hydroxide on each chloride. 

(d) Optional. Test unknown solutions for (1) a chloride and 

(2) lead, silver, and mercurous compounds. Note each result. 

Write answers to these questions in your laboratory notes. 
(1) In what are these three chlorides insoluble? (2) How 
could the three chlorides be separated from one another? 

(3) What is a test for (a) a soluble chloride, (b) an unknown 
solution supposed to contain a chloride, (c ) a lead compound, 
(d) a silver compound, ( e ) a mercurous .compound, (/) lead 
chloride, (g) silver chloride, ( h ) mercurous chloride ? (4) How 
can a chloride be distinguished from a sulfate? 

SUPPLEMENTARY EXERCISES ON CHLORINE 
AND HYDROCHLORIC ACID 

Supplementary Exercise 19 — Preparation and Properties of 
Chlorine — Teacher’s Exercise 

Materials. — Concentrated hydrochloric acid, 10 gm. of man¬ 
ganese dioxide, and as in Exercise 23 (except potassium per¬ 
manganate). 

Apparatus. — As in Fig. 37. If desired, the optional apparatus 
shown in Fig. 38 may be used. 

Caution. — As in Exercise 23. 

I. Preparation. — Slip the manganese dioxide into the 
flask. Arrange the apparatus as shown in Fig. 37. Intro- 

53 


duce enough concentrated hydrochloric acid through the 
dropping tube B to cover the manganese dioxide. Heat the 
flask A gently with a small flame. Avoid heating so high 
that steam or hydrogen chloride is evolved. 

Chlorine passes into the bottle G, which should be removed 
when full (as seen by the color) and covered tightly with a 
piece of filter paper; the bottle may be easily removed by 
holding the paper cover F in one hand and pulling the bottle 
G aside, bending the whole delivery tube at the same time at 
the rubber connection D. If the evolution of gas slackens, 
introduce more acid. Collect four bottles, and proceed at 
once as in II. 

II. Properties. — As in Exercise 23, ( a ) to (e). 


Supplementary Exercise 20 — Chlorine Water — 
Teacher’s Exercise 

Materials. — Chlorine water, litmus paper, colored cloth or paper, 
ink-stained cloth, gold leaf (for ( b )). 

Obtain about 50 cc. of chlorine water, or prepare it by 
letting the gas bubble for fifteen minutes or more through a 
bottle half full of water. 

(a) Try the bleaching action of chlorine water on litmus 
paper, bright colored cloth or paper (which is not decolorized 
by water alone), and a piece of ink-stained cloth. Note the 
results. 

(i b ) Determine the solvent power as follows: Stand a test 
tube in the rack. Moisten the end of a glass rod, touch it to a 
small piece of gold leaf, hold the rod with the adhering gold 
leaf inside a test tube, and wash the gold leaf into the test 
tube by pouring about 15 cc. of chlorine water down the rod. 
Remove the rod. Warm the test tube gently and shake 
until a definite change in the gold is observed. Note the 
final result. 

Write answers to these questions in your laboratory notes. 

(1) What effect has chlorine water on many colored substances f 

(2) On gold f (3) What compound is formed in (b) ? 

54 


Supplementary Exercise 21 — Bleaching with Bleaching 
Powder — Teachers Exercise 

Materials. — Bleaching powder, dilute sulfuric acid, colored 
cloth. 

Apparatus. — 3 dishes (small), glass rod. 

Put a little bleaching powder into one dish and add 
enough water to make a thin paste. Fill the second dish 
one-third full of dilute sulfuric acid, and the remaining one 
full of water. 

Press the lower half of the colored cloth into the bleaching 
powder with the glass rod, and then into the acid, passing 
it back and forth several times. Finally wash the cloth 
thoroughly in the water, squeeze out the excess of water, and 
compare the upper and lower parts of the cloth. Note the 
change in color. Dry the cloth and paste it in your labora¬ 
tory notebook. (If the change is not marked, try other 
kinds of cloth.) 

Write a brief description of this exercise in your laboratory 
notes. 

Supplementary Exercise 22 — Preparation and Properties 
of Hydrogen Chloride 

Materials. — Sodium chloride, concentrated sulfuric acid, silver 
nitrate solution, litmus paper, ammonium hydroxide. 

I. Preparation. — Put a few grams of sodium chloride in a 
test tube, stand the tube in the rack, and carefully add several 
cubic centimeters of concentrated sulfuric acid. Hydrogen 
chloride is evolved. 

II. Properties. — ( a ) Hold a piece of blue litmus paper at 
the mouth of the test tube. Observe the result. 

( b ) Blow the (moist) breath across the mouth of the tube. 
Hold a piece of wet filter paper in the gas. Observe the result 
in each case. 

(c) Hold a glass rod moistened with ammonium hydroxide 
in the gas. Observe the result. 

(d) Moisten a clean glass rod with silver nitrate solution 
and hold it in the gas. Observe the result. 

55 


Write answers to these questions in your laboratory notes. 
(1) What is (a) the verbal and (b) the chemical equation 
for the reaction in I ? (2) What causes the change in II (a) 

and ( b ) f (3) What solid compound is formed in II (c) f What 
is the chemical equation f (4) As in (3) applied to II {d)f 

Supplementary Exercise 23 — Aqua Regia — Teacher’s 
Exercise 

Materials. — Gold leaf, concentrated nitric and hydrochloric 
acids. 

Touch a small piece of gold leaf with the end of a moist 
glass rod, and wash the gold leaf into a test tube by pouring 
a few cubic centimeters of concentrated hydrochloric acid 
down the rod. Warm gently. Note if the gold dissolves. 

Wash another piece of gold leaf from a clean glass rod into 
another test tube with concentrated nitric acid. Warm as 
before, and note if the gold dissolves. 

Prepare aqua regia by pouring the contents of one tube 
cautiously into the other. Warm gently, and note if the 
gold dissolves. 

Write a brief account of this exercise in your laboratory notes. 
Answer also these questions. (1) What compound of gold is 
formed by its interaction with aqua regia t (2) Would chlorine 
water act like aqua regia on gold f 

Supplementary Exercise 24 — Types of Chemical Change — 
Teacher’s Exercise 

Materials. — For (a) mercury, iodine; for ( e ) optional. 

(a) Direct combination. Put a drop of mercury in a 
mortar, add a small fragment of iodine, grind the two to¬ 
gether, and note the result. The product is a compound of 
mercury and iodine. 

(b) Direct decomposition. As in Supplementary Exercise 1. 

(c) Simple replacement. As in Supplementary Exercise 8. 

(d) Double decomposition. As in Supplementary Exer¬ 
cise 9 (b). 


56 


(e) Optional. (1) Heat magnesium in air. (2) Put a 
clean nail in copper sulfate solution. (3) Mix silver nitrate 
and calcium chloride solutions. (4) Heat lead nitrate in a 
test tube. (5) Mix calcium chloride and sodium carbonate 
solutions. Note each result. 

Write equations for (a) to (d) in your laboratory notes. 

Write also (if available) the results in (e) with equations , 
and state what type of chemical change each numbered part 
illustrates. 


AIR — NITROGEN 


Exercise 27 — Per Cent of Oxygen in Air — 
Teacher’s Exercise 

Materials. — Solutions of pyrogallic acid (10 per cent) and sodium 
hydroxide (50 per cent). 

Apparatus. — As in Fig. 39 ; pneumatic trough half full of water 
at room temperature, 250 and 25 cc. graduated cylinders. The 
bottle holds about 250 cc. and is provided with a tightly fitting 
one-hole rubber stopper through which passes a glass plug. The 
plug is about 10 cm. (4 in.) long and is made by 
closing both ends of a glass tube; it should fit 
tight. 

Object. — To find the volume of oxygen 
absorbed from a measured volume of air. 

Copy the form of Record, as given below, 
in your notebook and enter each volume as 
soon as the readings are made. 

First find the volume of the bottle. Fill the Fig. 39. — Appa- 
pneumatic trough with water and add water, ^atus 
if necessary, to bring the temperature to that oxygen in air 
of the room. Fill the bottle full of water 
from the pneumatic trough. Push the stopper into the 
bottle as far as it will go, insert the glass plug until the inner 
end is flush with the inner surface of the stopper, and draw 
a line around the stopper with a pencil to mark its position 
(Fig. 39). Remove the plug and then the stopper carefully, 
to avoid loss of water. Pour water from the bottle into the 

57 







250 cc. graduate until the graduate is full (to the 250 cc. 
mark) or the bottle is empty; read the volume. If the bottle 
holds more than 250 cc., the rest of the water in the bottle 
may be poured into the 25 cc. graduate. Enter the total 
volume of the bottle in the Record. 

Record 

a. Volume of bottle. cc - 

b. Volume of original solution (total).. cc - 

c. Volume of air taken (a — b) . cc. 

d. Volume of final liquid. cc - 

e. Volume of water which entered (d — b) . . cc. 

/. Per cent of water which entered (e - 5 - c) . . 

Therefore: — 

g. Per cent of oxygen in the sample of air . . . 

h. Per cent of nitrogen (100 — g) . 

Measure exactly 10 cc. of the pyrogallic acid in the 25 cc. 
graduate, and pour it carefully into the bottle. Measure 
also exactly 20 cc. of the sodium hydroxide solution, and pour 
it into the bottle. (Caution. — The sodium hydroxide solu¬ 
tion is corrosive. Do not spill it on the hands or clothing.) 
Insert the rubber stopper (with its plug) quickly to the proper 
mark. 

Shake the bottle vigorously for a few minutes, and then 
invert it and watch the surface of the liquid for bubbles of air, 
which will enter if the apparatus leaks. If a leak is detected, 
ask the Teacher for directions before proceeding. If the 
apparatus is tight, continue the shaking for about half an hour. 
During this operation the oxygen is absorbed by the solution. 

Place the bottle on its side beneath the water in the pneu¬ 
matic trough, inclining it slightly so that the lower edge of the 
bottle rests upon the bottom of the trough and the hole in 
the stopper is beneath the surface of the water. With one 
hand grasp the bottle firmly by the neck and stopper, and 
with the other gradually pull out the plug to let the water 
run in. Water will run in quickly to fill the space left by the 
oxygen. Take care (1) not to pull out the stopper, (2) not 
to let any of the solution run out, and (3) also to keep the 

58 








hole in the stopper constantly beneath the surface of the 
water. After the water has stopped running in, lift out 
the bottle, and measure carefully the volume of the liquid in 
the bottle by pouring it into a graduate. Complete the 
entries in the Record. 

Note. — This exercise disregards the argon and carbon 
dioxide in air. 

« 

Write a brief account of this exercise in your laboratory notes. 

SUPPLEMENTARY EXERCISES ON AIR 

Supplementary Exercise 25 — Air and Combustion 

Materials. — Wood, paper, candle. 

Apparatus. — Two blocks of wood, lamp chimney. 

(a) Set fire to a small piece of wood, drop it while burning 
into a bottle of air, and cover the bottle at once with a block 
of wood. Note the final result. 

( b ) Proceed as in (a), using a piece of paper and another 
bottle. Note the final result. 

(c) Attach a short candle to a block of wood with melted 
candle wax. Stand a lamp chimney tightly over the lighted 
candle. Note how the flame is affected. 

(, d ) Hold the chimney a short distance (1 cm. or 0.5 in.) 
above the lower end of the (lighted) candle. Note if the 
candle continues to burn. Keep the chimney in the same posi¬ 
tion and cover the top with a block of wood. Note the result. 

Write answers to these questions in your laboratory notes. 
(1) What is your conclusion from these exercises about the 
relation of air to combustion f (2) Of oxygen to combustion f 

Supplementary Exercise 26 — Water Vapor and Carbon 
Dioxide in Air 

Materials. — Calcium chloride, calcium hydroxide solution. 

(a) Place a piece of calcium chloride on a glass plate or a 
block of wood, and let it remain exposed to the air for an hour 
or more. Observe the result. 

59 


( b ) Pour 25 cc. of calcium hydroxide solution into a bottle, 
and let it stand exposed to the air for an hour or more. 
Examine the surface of the liquid. 

Write in your laboratory notes the results observed in (a) and 
(i b ) and state how they show the presence of water vapor and 
carbon dioxide in air. 


Supplementary Exercise 27 — Preparation and Properties of 
Nitrogen — Teacher’s Exercise 

Materials. — Ammonium chloride, sodium nitrite, joss stick, iron 
thread, sulfur. 

Apparatus. — As in Fig. 40, three bottles. 

I. Preparation. — Weigh 8 gm. of ammonium chloride 
and 10 gm. of sodium nitrite, put them in the flask, add 50 cc. 

of water, and shake well. 
Arrange the apparatus, as 
in Fig. 40, to collect the 
gas over the water. Fill 
three bottles with water 
and invert one in the 
trough ready to slip into 
the position of G. Have 
two more bottles ready 
to replace this one. Fill 
the cup of the dropping 
funnel with water. 

Heat the flask gently 
with a low flame, and as 
soon as the gas bubbles 
regularly through the 
water, slip the bottle over 
the hole in the support. 
Heat gently, but enough to keep the gas bubbling slowly 
through the water. Collect three bottles of nitrogen. 

Caution. — If the mixture in the flask begins to froth or the 
gas comes off too rapidly, remove the flame and let in a little 
water. If it continues to froth, pinch the clamp to let out the 

60 



Fig. 40. 


Apparatus for preparing 
nitrogen 


















excess of gas ; as soon as the frothing lessens, close the clamp 
and heat gently. When the last bottle of nitrogen has been 
collected, remove the delivery tube from the water. Proceed 
at once with II. 

II. Properties. — (a) Thrust a blazing joss stick into a 
bottle of the gas. Observe the result. 

( b ) Put a piece of sulfur in a deflagrating spoon, light the 
sulfur, lower it into a bottle of nitrogen, and keep it there 
about half a minute. Observe the result. Withdraw, and 
observe the result. If the sulfur is still burning, repeat. 
Note the result. 

(c) Wind one end of a copper wire around a wad of iron 
thread, heat a few strands, and quickly thrust the glowing 
iron into a bottle of nitrogen. Observe the result. 

Write in your laboratory notes (1) the equation for I, and 
(2) a summary of the properties of nitrogen. 

Optional Exercises 

1. Describe briefly the preparation of nitrogen. 

2. Sketch the apparatus. 

3. Compare the characteristic properties of nitrogen with 
those of oxygen found by similar exercises. 


ACIDS, BASES, AND SALTS 

^Exercise 28 — Behavior of Oxides with Water 

Materials. — Sulfur, calcium oxide (lime), litmus paper. 
Apparatus. — Deflagrating spoon. 

(a) Put a little water in a bottle. Set fire to a small 
piece of sulfur in a deflagrating spoon and lower into the 
bottle. Let it burn a minute or two, then extinguish the 
flame by dipping the spoon into the water. Remove the 
spoon, cover the bottle with the hand, and shake well. Dip 
a glass rod into the liquid, draw the moistened end across a 
piece of blue litmus paper, and observe the change in color. 
This change in the color of blue litmus is caused by acids; 

61 


in this case the acid is sulfurous acid, which was produced by 
the combination of sulfur dioxide — an acidic oxide — and 
water. 

(6) Boil a small piece of calcium oxide with a little water 
in a test tube. Test with red litmus paper as in (a). If the 
result is indifferent, put the paper in the test tube and shake 
well. Observe the result in a minute or two. Compare with 
(a). This change in the color of red litmus is caused by bases ; 
in this case the base is calcium hydroxide, which was produced 
by the combination of calcium oxide — a basic oxide — and 
water. 

Write a brief account of this exercise in your laboratory notes, 
including the equations, both verbal and chemical for the com¬ 
bination of these oxides with water. 


Exercise 29 — Neutralization 


Materials. — Sodium hydroxide (solid), dilute hydrochloric acid, 
blue litmus paper. 

Apparatus. — As in Fig. 41; glass rod. 

Dissolve a small piece of sodium hydroxide in an evaporat¬ 
ing dish one-third full of water. Add a little dilute hydro¬ 
chloric acid, and stir thoroughly ; Continue 
to add the acid very slowly and stir, until 
a drop of the well-mixed solution taken 
from the dish by a clean glass rod just 
reddens blue litmus paper. If the dish 
becomes too full, pour out some of the 
solution. 

Evaporate the solution to dryness by 
heating the dish on a gauze-covered ring 
(Fig. 41). Heat carefully toward the end 
to prevent spattering. When dry (or 
nearly so), heat strongly until the yellow 
color (due to the slight excess of hy¬ 
drochloric acid added) disappears, then 
moisten the whole residue carefully with 
a little warm water, and heat again to evaporate the last 
traces of acid ; add and evaporate two portions of water. 

62 


CK3(pJlg”^ 




Fig. 41. — Evaporat¬ 
ing a solution 








Test small portions of the residue. (1) Apply the litmus 
test, and note if the residue has acid, basic, or neutral prop¬ 
erties. (2) Taste a little, and note if it has the character¬ 
istic property of an acid, base, or salt. (3) Dissolve some in 
water and test the solution for a chloride. Note the result. 
(4) Test for sodium by heating a little on a test wire in the 
flame. Note the result. 

Write a brief description of this exercise in your laboratory 
notes, including answers to: (1) Is the residue an acid, base, or 
salt f (2) What is the name of the residue f (3) What is the 
equation for the reaction f 

Optional Exercises 

1. Define neutralization. Write a typical equation. 

2. If potassium hydroxide and nitric acid were used, what 
salt would be formed? Write the equation. 

3. As in 2, if ammonium hydroxide and sulfuric acid were 
used? Write the equation. 


Exercise 30 — Neutralization by Titration — 
Teacher’s Exercise 


Materials. — Phenolphthalein solution, and 
solutions of hydrochloric acid and sodium 
hydroxide (the latter of known concentration 
and obtained from the Teacher). 

Apparatus. — Burettes, beakers, and glass rod 
as in Fig. 42, waste beaker. 

Object. — To find the weight (in grams) 
of the compound HC1 in 1 cc. of a solu¬ 
tion of hydrochloric acid (i.e., HC1 dis¬ 
solved in water) by neutralizing the acid 
with a solution of sodium hydroxide of 
known concentration. 

Copy in your laboratory notes the form 
of Record given below, and enter each 
volume as soon as the reading is made. 

Fill each burette (or start with each full) 
63 



for accurate neu¬ 
tralization 















— one with the acid solution and one with the base solution 
(Fig. 42). Label each burette. Be sure the tip of the burette 
is free from air bubbles. (To remove air bubbles, open the 
stopcock slightly, and shake the burette up and down 
quickly.) Place the waste beaker under each burette in 
turn and allow the solution to run out slowly until the 
bottom of the meniscus rests on the 0 
line when the eye is on a level with the 
same line. (See Fig. 43.) Set the waste 
beaker aside. 

Put a clean beaker under the base burette 
and let exactly 15 cc. run into the beaker; 
enter in I in the Record. Remove the 
beaker, add 2 or 3 drops of phenolphthalein 


1^3 


Fig. 43.—Meniscus solution, put the beaker under the acid 
— correct reading burette, and let the acid solution run in 
drop by drop, stirring constantly with the 
clean rod until the red color (caused by the base) just dis¬ 
appears and the solution becomes colorless (caused by the 
very slight excess of acid). Read the exact volume of acid 
solution added and enter in I. 


Record 

I. NaOH sol. 0-15 = 15 

HC1 sol. 0 - = 1 cc. NaOH sol. = cc. HC1 sol. 

II. NaOH sol. 15 - 30 = 15 

HC1 sol. - = 1 cc. NaOH sol. = cc. HC1 sol. 

III. NaOH sol. 30 - 45 = 15 

HC1 sol. - = 1 cc. NaOH sol. = cc. HC1 sol. 

1 cc. NaOH sol. = cc. HC1 sol. (average) 

1 cc. of NaOH solution contains gm. NaOH 

1 cc. of HC1 solution contains gm. HC1. 

Pour the solution out of this beaker, wash the beaker, and 
proceed, as before, to neutralize a second 15 cc. of NaOH solu¬ 
tion. Enter in II. 

Wash the beaker and proceed with a third 15 cc. of NaOH 
solution. Enter in III. 


64 







Calculation. — Our problem.is to calculate the number of 
grams of HC1 in 1 cc. of the solution of hydrochloric acid 
used in this exercise. 

(a) First write the equation for the reaction, thus,: — 

HC1 + NaOH = NaCl + H 2 0 
36.5 40 58.5 18 

This equation means that 36.5 gm. of HC1 are needed to 
neutralize 40 gm. of NaOH. 

(i b ) Next calculate (from I, II, III, above) the average 
number of cubic centimeters of hydrochloric acid solution 
which would be neutralized by 1 cc. of sodium hydroxide 
solution. For example, suppose you find 1.5 cc. HC1 sol. = 
1 cc. NaOH sol. (Your result, of course, may be different 
from this value.) 

(c) Find out from the Teacher the concentration of the 
sodium hydroxide solution. For example, suppose 1 cc. of 
the given sodium hydroxide solution contains 0.00641 gm. 
of NaOH. 

( d ) Now from the equation in (a) we see that 40 gm. of 
NaOH require 36.5 gm. of HC1. Then the number of grams 
of HC1 required by 0.00641 gm. of NaOH would be found by 
the proportion 

40 : 36.5 :: 0.00641: x x = 0.00585 
(Your result depends on the concentration of your NaOH 
solution.) But 0.00585 gm. of HC1 would be dissolved in 
1.5 cc. of hydrochloric acid (according to our supposition in 
(6)). Therefore, to find the number of grams of HC1 that 
would be dissolved in 1 cc. of the acid solution, we divide 
0.00585 by 1.5, i.e. 0.00585 1.5 = 0.0039. Ans. 0.0039 

gm. of HC1 in 1 cc. 

From your results of titration and the known concentra¬ 
tion of the NaOH solution, calculate the weight (in grams) 
of the compound HC1 in 1 cc. of the given hydrochloric acid 
solution. Enter the result in your Record. 

If time permits, write a brief account of this exercise in your 
laboratory notes (in addition to your Record), and also draw 
the apparatus. 

65 


Exercise 31 — Preparation of Salts 

Materials. — Calcium, calcium oxide and carbonate, lead 

oxide; solutions of lead nitrate, sodium sulfate, and sodium 

hydroxide. 

A. Salts Soluble in Water, (a) An acid and a metal. 
Put a small piece of calcium in an evaporating dish, add a 
little dilute hydrochloric acid, stand the dish on a gauze- 
covered ring, and heat gently in the hood until the calcium 
disappears, adding more acid if necessary. Then evaporate 
the solution to dryness; heat gently toward the end to pre¬ 
vent spattering. Moisten the residue with water, and 
evaporate again to dryness. Heat the residue until no more 
fumes of hydrochloric acid are evolved. Let the dish cool, 
and loosen the solid with a glass rod. 

Test small portions of the solid residue for (1) calcium 
(flame test), and (2) a chloride. Note the results. 

(6) An acid and an oxide. Proceed as in (a), using hydro¬ 
chloric acid and a small piece of calcium oxide. Test the 
final residue as in (a). Note the results. 

(c) An acid and a carbonate. Proceed as in (a), using 
hydrochloric acid and a small piece of calcium carbonate. 
Test the final residue as in (a). Note the results. 

(d) An acid and a base. Proceed as in Exercise 29. 

B. Salts Insoluble in Water, (a) An acid and a salt. 
Add 5 cc. of sulfuric acid to 5 cc. of lead nitrate solution. 
Note the formation of an insoluble salt. Observe its color, 
fineness, heaviness, and insolubility. 

(6) A salt and a salt. Add 5 cc. of sodium sulfate solution 
to 5 cc. of lead nitrate solution. Note and observe as in (a). 

( c ) An acid and an oxide. Add 5 gm. of lead oxide to 
10 or 15 cc. of dilute hydrochloric acid, heat, let any un¬ 
changed solid settle, pour the hot liquid into another test 
tube, and cool in running water. Note and observe as in (a). 

(d) An acid and a carbonate. Proceed as in (c), using 
lead carbonate. Note and observe as in (a). 

C. Normal Salt. Put 10 cc. of dilute sulfuric acid in an 
evaporating dish and neutralize it exactly with sodium 
hydroxide (see Exercise 30). Evaporate to about two-thirds 

66 


its volume, let the solution crystallize. The solid product is 
a normal salt. 

D. Acid Salt. Proceed as in C with the neutralization, 
then add 10 cc. more of the sulfuric acid, evaporate to about 
two-thirds its volume, and let it crystallize. The solid 
product is an acid salt. 

Write a brief account of this exercise in your laboratory notes , 
giving under each lettered part the name and formula of the salt 
formed. 

Write also equations for all the reactions. 


SUPPLEMENTARY EXERCISES ON ACIDS, 
BASES, AND SALTS 

Supplementary Exercise 28 — General Properties of Acids 

Materials. — Sulfuric, hydrochloric, and nitric acids, litmus 

paper (both colors), magnesium ribbon, sodium carbonate, lime- 

water. 

Fill three test tubes half full of water; add about 5 cc. of 
dilute sulfuric acid to one, of hydrochloric acid to another, 
and of nitric acid to the third. Shake the test tubes thor¬ 
oughly, and label each. 

(a) Dip a clean glass rod into each acid successively and 
cautiously taste it. Note the taste. 

(&) Dip a clean glass rod into each acid successively and 
put a drop on both kinds of litmus paper. Note the decided 
change in color. The change is characteristic of acids. 

(c) Pour out the very dilute solutions of the acids and 
replace the hydrochloric and sulfuric acids with the dilute 
acid from the stock bottle. Omit the nitric acid. Slip a 
small piece of magnesium ribbon into each test tube. Note 
the result. If not conspicuous, warm each gently. . Test 
the most obvious product by holding a lighted match inside 
of each tube. Note the result. 

(d) (1) Fill a test tube half full of dilute sulfuric acid, 
have ready a lump of sodium carbonate to add to the acid. 
Dip a glass tube just below the surface of some limewater, 

67 


and press the finger down upon the outer end of the tube 
to hold in the limewater. Lift out the tube, drop the sodium 
carbonate into the acid, and hold the limewater tube in the 
‘escaping gas (Fig. 44). Note the 
effect on the limewater. 

(2) Proceed as in (1) with the other 
two acids. 

Write in your laboratory notes a 
summary of the properties of acids. 

Write also an explanation of the 
chemical change in ( c) and ( d ). 


Supplementary Exercise 29—General 
Properties of Bases 



Fig. 44. — Testing for car¬ 
bon dioxide with a lime- 
water tube 


Materials. — Sodium hydroxide and po¬ 
tassium hydroxide solutions, ammonium 
hydroxide, litmus paper (both colors). 


Prepare a very dilute solution of each base as in Supple¬ 
mentary Exercises 28. 

(a) Cautiously taste each solution by touching to the tip 
of the tongue a rod moistened with each. Note the result. 

( b ) Test each solution with litmus paper (both colors). 
Note the result. 

(c) Rub a little of each undiluted solution from the stock 
bottle between the fingers, and note the feeling. 

Write in your laboratory notes a summary of the properties 
of bases. 

Write also a comparison of the corresponding tests for acids. 


Supplementary Exercise 30 — Two Properties of Many Salts 

Materials. — Litmus paper (both colors), dilute solutions of 
chemically pure sodium chloride, potassium nitrate, potassium 
sulfate, barium chloride, potassium chlorate, potassium bromide, 
and strontium nitrate. 

(a) Test the solutions with litmus paper. Note the result 
in each case. Compare the litmus reaction of these salts 
with the reaction of acids and bases. 

68 









(by Dip a clean glass rod into each solution (except barium 
chloride) successively and cautiously taste it. Do not swallow 
the liquid. Note the taste. 

Write a brief statement in your laboratory notes of these two 
properties of many salts. 


IONIZATION AND IONS 


Exercise 32 — Electrolytes and Non-Electrolytes — 
Teacher’s Exercise 

Materials. — Hydrochloric acid, sodium hydroxide, calcium 
chloride, sugar, alcohol, glycerin. 

Apparatus. — As in Fig. 45. A is a jar for the solution, B and C 
are electrodes of aluminum which are supported on the top of the 
jar by a strip of wood. D is an electric light bulb which is con¬ 
nected with the wire from the electrode B and with one end of the 
wire E. The wire from the electrode C and the other end of the 
wire E are connected with a direct street current (reduced), a 
storage battery, or 4 
dry cells. 

Object. — To find out 
whether a substance 
forms a conducting 
or a non-conducting 
solution. 



Fig. 45. •— Apparatus for showing what 
solutions conduct electricity 


Construct and ar¬ 
range the apparatus 
as in Fig. 45. 

(a) Fill the jar two- 
thirds full of dilute hydrochloric acid, see that all connec¬ 
tions are tight, and turn on the current. Note whether 
the bulb glows. 

(5) Proceed as in (a), using successively solutions of sodium 
hydroxide, calcium chloride, sugar, alcohol, and glycerin. 
Clean the electrodes and jar each time. Observe each 
result. 


69 












Write a brief account of this exercise in your laboratory notes. 
Write also answers to these questions. (1) What substances 
form solutions which conduct electricity f (2) What substances 
form non-conducting solutions f (3) What is the name of the 
classes of substances in (1) ? 

Exercise 33 — Electrolysis of Copper Sulfate Solution — 
Teacher’s Exercise 

Materials. — Copper sulfate solution, joss stick. 

Apparatus. — Hofmann apparatus, storage battery or reduced 
direct current. 

Fill the Hofmann apparatus (Fig. 46) 
full of copper sulfate solution. Connect 
with a storage battery or a reduced direct 
current. Turn on the current and let it 
run until about 10 cc. of gas collects. 

Note at which electrode (anode or 
cathode) (a) a gas was liberated, and 
(6) a solid deposited. 

Have a glowing joss stick ready, let out 
a little gas, and test it with the glowing 
joss stick. Note what the gas is. Also 
note what the solid is. 

Write a short account of this exercise in 
your laboratory notes. 

Write also answers to these questions. 

(1) What ions are in copper sulfate solution ? 

(2) To what electrode does each kind of ion 

migrate? (3) What happens when the ions 

Fig. 46. —Hofmann reac } l ifo electrodes f (4) What secondary 
apparatus tor elec- . i . j a 

trolysis action takes place at one electrode / 

Exercise 34 — Reversible Reactions 

Materials. — Antimony trichloride and sodium hydrogen sulfate 
(NaHS0 4 ) solutions. 

(a) Pour a little antimony trichloride solution into a test 
tube three-fourths full of water. Note the precipitate 

70 















(antimony oxychloride), especially its color and texture. 
Shake well. To a portion of the suspended precipitate add 
a little concentrated hydrochloric acid, drop by drop, shaking 
constantly, until a definite change occurs. Note the result. 

(6) To 10 cc, of concentrated sodium hydrogen sulfate add 
concentrated hydrochloric acid slowly until a definite change 
occurs. Note the result. 

Write a brief description of (a) and ( b) in your laboratory 
notes. 

Write the equation for the reversible reaction in (a) and (b) 
both in words and in formulas. 


Exercise 35 — Colored and Colorless Ions — Teacher’s 
Exercise 

Materials. — Solutions (dilute) of copper sulfate, copper nitrate, 
copper bromide, nickel chloride, nickel sulfate, cobalt chloride, 
cobalt nitrate, potassium dichromate, ammonium dichromate, 
sodium dichromate, potassium chromate, potassium perman¬ 
ganate. 

(a) Observe the color of the copper solutions. Conclude 
to what ion the color is due. Give its ionic name and 
formula. 

(i b ) As in (a) with the nickel, etc., solutions. 

Copy this table in your laboratory notes and fill in the items: 


Colored and Colorless Ions 


Cations 

Anions 

Name 

Formula 

Color 

Name 

Formula 

Color 

1 



1 



2 



2 



3 



3 



etc. 



etc. 




71 


















SUPPLEMENTARY EXERCISES ON IONIZATION 
AND IONS 

Supplementary Exercise 31 — Electrolysis of Copper Sulfate 
Solution (Short Method) — Teacher’s Exercise 

Material. — Dilute copper sulfate solution. 

Apparatus. — Small battery jar (or beaker ) i two electrodes (pieces 
of electric light carbon) and connection wires, storage battery (or 
other source of direct electric current). ■ 

Fill the battery jar about two-thirds full of dilute copper 
sulfate solution. Wind the end of a piece of the wire around 
one end of each electrode and hang the electrodes in the 
solution by bending the wire over the edge of the jar (or 
supporting them by a strip of wood which rests across the top 
of the jar). Connect the ends of the wires with the storage 
battery (or other source of direct electric current). 

Before turning on the current (or making the final con¬ 
nection), examine each electrode and note the absence of a 
deposit. Turn on the current and observe at which electrode 
bubbles of gas form. Let the current run about ten minutes, 
and then examine each electrode. Compare with their 
appearance before the electrolysis took place. Note upon 
which electrode (anode or cathode) there is a deposit. Note 
the deposit. 

Write in your laboratory notes a brief account of the electrolysis 
of copper sulfate in terms of the ionization theory, using a sketch 
of the apparatus in your account. 

Supplementary Exercise 32 — Electrolysis of Sodium 
Sulfate Solution — Teacher’s Exercise 

Materials. — Sodium sulfate solution, neutral litmus solution, 
joss stick, wax taper. 

Fill the Hofmann apparatus (Fig. 46) full of sodium sulfate 
solution colored with neutral litmus solution. Proceed as in 
Exercise 33. Let the current run until the smaller volume 
of gas measures about 10 cc. Observe the color of the 
solution in each tube; also the relative quantity of gas. 
Test the gases as in Exercise 33. Note the result. 

72 


Write in your laboratory notes an interpretation of the 
electrolysis of sodium sulfate by the theory of ionization. 

Write also answers to these questions. (1) What is the 
name of each gasf (2) At which electrode was each gas 
liberated f (3) Why was the color changed in each tube? 

Supplementary Exercise 33 — Chemical Behavior of Solu¬ 
tions of Acids, Bases, and Salts (Testing for Ions) 

Materials. — For (a) hydrochloric acid, solutions of chlorides of 
barium, calcium, sodium; for (b) sulfuric acid, solutions of sul¬ 
fates of copper, sodium, zinc; for (c) solutions of hydroxides of 
sodium and potassium; also solutions of silver nitrate, silver 
sulfate, barium chloride, barium nitrate, and zinc sulfate. 

(a) (1) Test separately a dilute solution of the substances 
enumerated in (a) by adding to each a few drops of silver 
nitrate solution. Note each result. Conclude what ion is in 
each tested solution. Enter each result in the table (see 
below) in your laboratory notes. 

(2) Proceed as in (1), using silver sulfate solution. Note 
and make the entries, as in (1). 

(b) (1) Proceed as in (a) (1), using barium chloride 
solution and the solutions enumerated in (6). Note, con¬ 
clude, and enter the results in the table. 

(2) Proceed as in (1), using barium nitrate solution in 
place of barium chloride. Note, conclude, and enter as 
before. 

(c) Add (1) a few drops of the solutions of hydroxides 
enumerated in (c) to zinc sulfate solution and then (2) an 
excess of each hydroxide. Note, conclude, and enter as 
before. 


Write the results of this exercise in tabular form in your 
laboratory notes , thus: — 


Substance 

Result 

Conclusion 





73 












Optional Exercises 

1. What ion is common to solutions of hydrochloric acid 
and chlorides ? Of sulfuric acid and sulfates ? 

2. Explain the general result in (a) and in (6) in terms of 
the theory of ionization. Also the results in ( c ) (1). 

3. What ion is common to all (a) barium salts and 
( b ) silver salts ? 

4. What ion other than potassium ion is in a solution of 
(a) potassium chloride, ( b) potassium chlorate, and ( c) po¬ 
tassium perchlorate? 

5. What ion is in solutions of (a) all acids and ( b ) all bases ? 

6. Make a list of the acids, bases, and salts used in this 
experiment and their corresponding ions, indicating the 
substances and ions by name and formula. 

Supplementary Exercise 34 — Hydrolysis of Certain 
Salts 

Materials. — Solutions of sodium carbonate, ferric chloride, 
aluminum sulfate, copper sulfate, zinc chloride. 

Test a solution of each salt with litmus paper (both kinds), 
and note the result. 

Write in your laboratory notes the effect of each dissolved salt 
on litmus. 

Write also answers to (1) What is hydrolysis f (2) What 
classes of salts undergo hydrolysis? 

AMMONIA 

^Exercise 36 — Preparation and Properties of Ammonia 

Materials. — Lime (calcium oxide), ammonium chloride, con¬ 
centrated hydrochloric acid. 

Apparatus. — As in Fig. 47. The test tube A is provided with a 
one-hole rubber stopper to which is fitted a glass tube B which 
reaches well up into the bottle C ; 3 bottles, pneumatic trough 
filled as usual. Optional forms of apparatus (as in Fig. 48) may 
be used. 

Caution. — Do not inhale ammonia (gas). Perform this 
experiment in the hood. 


74 


I. Preparation. — Weigh 10 gm. of lime and 10 gm. of 
ammonium chloride, and mix them thoroughly on a piece of 
paper. Slip the mixture into A (Fig. 47), and add a little 
water, thereby transforming the calcium 
oxide into calcium hydroxide. Mix well. 

Quickly insert the stopper with its tube, 
and clamp A as in Fig. 47. Stand the 
bottle C over the tube B. 

If the simpler apparatus (Fig. 48) is 
used, put about 5 gm. of each ingredient, 
together with the water, in the lower 
test tube. Heat this tube and collect 
the gas in the upper tube. 

Heat A gently with a low flame. 

Begin to heat the test tube near the 
end and slowly work forward toward 
the delivery tube. Ammonia (gas) will 
pass up into the bottle, which should be removed, when full, 
covered tightly with a glass plate or filter paper, and stood 
mouth downward on the desk. A piece of moist red litmus 

paper held near the mouth will 
show (by change in color) when 
the bottle is full. Do not smell 
at the mouth of the bottle. Collect 
two bottles of the gas. 

II. Properties. — ( a ) Test the 
gas in one bottle, or test tube, 
with a blazing j oss stick. Observe 
the result. 

( b ) Invert the same bottle in 
the pneumatic trough, and shake 
it vigorously, taking care to keep 
the mouth under water. Observe 
the change inside the bottle. 
Cover the mouth of the bottle 
with the hand or filter paper, 
invert, and stand upright on the desk. Test the contents 
of the bottle with litmus paper (both colors), and note 
the result. 



Fig. 48. — Simple 
forms of apparatus 
for preparing am¬ 
monia (gas) 



Fig. 47.—Apparatus for 
preparing ammonia 


75 
























(c) Pour a few drops of concentrated hydrochloric acid 
into an empty, warm, dry bottle. Rotate the bottle until 
the inside is well moistened with the acid. Cover it with a 
glass plate, invert it, and stand it upon a covered bottle of 
ammonia (gas). Remove both plates at once, and hold the 
bottles together by grasping them firmly about their necks. 
Observe the result, especially the evidence of the chemical 
action and the white substance. 

Write in your laboratory notes (1) the equation for I, (2) a 
summary of the properties of ammonia based on II, (3) a 
statement of other observed properties of ammonia, e.g. color, 
odor, specific gravity, behavior with litmus, and (4) the test for 
ammonia. 

Answer also (5) What is a test for ammonium compounds? 
(6) What is the equation for II (c) ? (7) What (besides the 

product ) is the evidence of chemical action in II (c) ? 


SUPPLEMENTARY EXERCISE ON AMMONIA 

Supplementary Exercise 35 — Preparation of 
Ammonia (Gas) from Various Substances 

Materials. — Gelatin, soda-lime, litmus paper, concentrated 
hydrochloric acid, substances enumerated in (6), ammonium 
sulfate, ammonium nitrate, sodium hycjroxide solution. 

(а) Mix a little gelatin and soda-lime on a piece of paper, 
slip the mixture into a test tube, attach a test tube holder, 
heat, and test the escaping gas with moist red litmus paper, 
or by a glass rod moistened with concentrated hydrochloric 
acid. Note the result. 

(б) Repeat (a), using soda-lime with hair, feather, leather 
scraps, or pieces of horn. Observe the result. 

(c) Dissolve a little ammonium chloride in water, add a 
little sodium hydroxide solution, warm gently, and test 
(cautiously) the liberated gas by its odor. Note the result. 

(d) Repeat (c), using ammonium sulfate and sodium 
hydroxide solution. Note the result. 

76 


(e) Proceed as in ( d ), using ammonium nitrate. Note the 
result. 

Write in your laboratory notes (1) the result of each lettered 
part of this exercise, and (2) the equations of (c), ( d ), (e). 

NITRIC ACID —NITROGEN OXIDES 

Exercise 37 — Preparation of Nitric Acid — 
Teacher’s Exercise 

Materials. — Sodium nitrate, concentrated sulfuric acid. 
Apparatus. — Glass stoppered retort, etc., as in Fig. 49. 

Caution. — Concentrated nitric acid and sulfuric acid are 
very corrosive. Do not spill them on the flesh or the clothing. 
Perform this exercise very 
carefully. 

Weigh 20 gm. of sodium 
nitrate and slip it into the 
retort through the tubu- 
lure (opening where the 
stopper goes). Fill the 
bottle nearly full of water. 

Put a large empty test 
tube into the bottle, insert 
the neck of the retort into 
the test tube, and clamp 
'the retort (upon the iron 
gauze) to the stand as 
shown in Fig. 49. Stand 
.’a funnel in the tubulure of the retort so that the end is well 
inside the bulb, and pour 20 cc. of concentrated sulfuric acid 
through the funnel. Remove the funnel and insert the 
stopper of the retort tightly. 

; Heat the retort gently as long as any nitric acid runs down 
the neck into the test tube. Then unclamp the retort and 
remove- the test tube carefully, taking great care not to get 
any nitric acid on the hands. 

; 77 



Fig. 49. —Apparatus for preparing nitric 
acid in the laboratory 













Note. — Allow the contents of the retort to cool, add a 
little water, boil until the solid in the bulb is reduced to a 
small bulk or dissolved, and pour the contents into a waste 
jar in the hood. 

Write a brief account of this exercise in your laboratory notes. 

^Exercise 38 — Properties of Nitric Acid 

Materials. — Concentrated nitric acid, quill toothpick, sulfur, 

barium chloride solution, zinc, copper, magnesium. 

(a) Observe the color of the concentrated nitric acid 
prepared in Exercise 37. Compare with the specimen of 
concentrated nitric acid in the bottle on the side shelf. 

(b) Hold a piece of wet filter paper at the mouth of a test 
tube of concentrated nitric acid. Observe the result. 

(c) Repeat (b), using a piece of filter paper moistened with 
ammonium hydroxide. Note the product. 

(d) Pour 5 cc. of concentrated nitric acid very carefully into 
a test tube, drop in a piece of a quill toothpick, and observe 
any change in the color of the quill. Heat very gently, and 
observe the effect on the quill. Note the final result. 

(e) Put about 1 gm. of sulfur in a test tube, add a little 
water and then very carefully 5 cc. of concentrated nitric 
acid. Attach the test tube holder, and boil cautiously — in 
the hood — for a few minutes. Add 10 to 15 cc. of water, 
filter the solution, if it is not clear, and test the filtrate for a 
sulfate by adding barium chloride solution. Note the result. 

(/) Stand three test tubes in the test tube rack, put a 
piece of zinc into one, copper into another, and magnesium 
ribbon (rolled into a ball) into the third. Add a little con¬ 
centrated nitric acid to each test tube. Observe the result. 
Test the gaseous product for hydrogen, and note the result. 
(Compare Exercise 39 II.) Note also the color of the copper 
solution. 

Write answers to these questions in your laboratory notes. 
(1) What property of nitric acid was shown by (a)? By (b)? 
By (c) ? By (<d ) ? By (e) ? (2) What is the result of (b) ? 

(3) How does the action in (/) compare with that of hydro¬ 
chloric acid and sulfuric acid ? 

78 


^Exercise 39 — Interaction of Nitric Acid and Copper (and 
Study of Nitric Oxide and Nitrogen Dioxide) 

Materials. — Copper (borings or fine pieces of sheet metal), con¬ 
centrated nitric acid, piece of copper wire (15 cm. or 6 in. long). 
Apparatus. — As in Fig. 50 . 

I. Preparation (Nitric Oxide). — Put 10 gm. of copper in 

the bottle A and arrange the apparatus to collect the gas over 
water (Fig. 50). Fill three bottles with water, and invert 
one of them in the p, 
trough. Have the 
others ready. ^ 2 ^ 

Dilute 25 cc. of 
concentrated nitric 
acid with an equal 
volume of water, and 
introduce just enough 
of this diluted acid 
through the dropping 
tube to cause gentle 
chemical action. If 
the action becomes 
too vigorous, add water immediately through the dropping 
tube ; if too weak, then add just enough of the diluted nitric 
acid to cause gentle action. 

Collect three bottles of the nitric oxide, remove, invert 
and cover them quickly with glass plates or tightly with 
moist filter paper. 

II. Properties. — (a) Observe the general properties of 
nitric oxide while covered. 

(6) Uncover a bottle. Observe the result. The brown 
gas is nitrogen dioxide. 

(c) Uncover another bottle, let the brown gas form, then 
pour in about 25 cc. of water, cover at once with the hand and 
shake vigorously, still keeping the bottle covered. Note 
whether the brown gas is soluble or insoluble in the water. 

( d ) With the third bottle, determine whether the gases 
will burn or support combustion. A convenient flame is a 
burning match fastened to a copper wire. (1) Uncover a 

79 



Fig. 50. — Apparatus for preparing nitric oxide 















bottle, quickly plunge the lighted match to the bottom of the 
bottle, and immediately replace the glass plate. Observe the 
result. (2) Remove the glass plate, let considerable brown 
gas form, lower a burning match into the brown gas, and 
observe the result. 

III. Copper Nitrate. — Filter the contents of the bottle 
A and test portions of the filtrate for (1) copper by adding a 
clean iron nail and noting the deposit, and (2) a nitrate as in 
Exercise 40. Note each result. 

Write in your laboratory notes a summary of the properties of 
nitric oxide and nitrogen dioxide. 

Write also answers to these questions. (1) What is the general 
chemical relation of the two gases to each other f (2) What is 
the equation for I and for II ( b ) ? 


^Exercise 40 — Test for Nitric Acid and Nitrates 


Materials. — Ferrous sulfate, sodium nitrate. 

(a) To 10 cc. of water add 1 or 2 cc. of concentrated nitric 
acid, and shake. Prepare a ferrous sulfate solution by wash- 
v _ "__l ing several crystals in cold water and dis¬ 
solving a clean crystal in 10 cc. of cold 
water. 

Pour this solution into the nitric acid. Mix 
well. Incline the test tube and pour about 
5 cc. of concentrated sulfuric acid down the 
inside of the tube. The sulfuric acid will sink 
through the other liquid. At the surface where 
the two solutions meet, a brown or black 
layer will appear (Fig. 51). Its formation 
serves as a test for nitric acid. 

(5) Proceed as in (a), using a concentrated solution of 
sodium nitrate instead of nitric acid. Note the result and 
compare with (a). 

Write the test for nitric acid and a nitrate in your laboratory 
notes. *- w — 


Fig. 51. — Test 
for nitric acid 
and nitrates 


so 






SUPPLEMENTARY EXERCISE ON NITROGEN OXIDES 


Supplementary Exercise 36 — Preparation and Properties 
of Nitrous Oxide — Teacher’s Exercise 

Materials. — Ammonium nitrate, wad of iron thread, copper 

wire, sulfur, joss stick. 

Apparatus. — As in Fig. 52. 

Put 10 gm. of ammonium nitrate in the flask A. Arrange 
the apparatus as shown in Fig. 52. The large test tube B 
remains empty. Be sure the apparatus 
does not leak. 

I. Preparation. —Heat the flask gently 
with a low flame. The ammonium 
nitrate melts at first and soon 
appears to boil, owing to the de¬ 
composition of the salt and escape 
of nitrous oxide, 
heat so that the 
nitrous oxide is 
slow. Notice 
the liquid which 
collects in B. 

Collect three 
bottles of nitrous 
oxide, covering 
each with a piece 



Regulate the 
evolution of 


Fig. 52. — Apparatus for preparing nitrous oxide 


of filter paper as soon as removed from the trough. When 
the last bottle has been collected and covered, remove the 
end of the delivery tube from the trough. 

II. Properties. — (a) Allow a bottle to remain uncovered 
for a few seconds. Note the difference between nitrous oxide 
and nitric oxide. 

( b ) Thrust a glowing joss stick into the same bottle of gas. 
Observe the result. 

(c) Put a piece of sulfur in a deflagrating spoon, light it, and 
lower the burning sulfur at once into another bottle of gas. 
Observe the result. 

( d ) Twist one end of the copper wire around a wad of iron 

81 





















thread. Heat the edge of the wad an instant in the flame and 
then lower it quickly into a bottle of the gas. Observe the 
result. 

Write answers to these questions in your laboratory notes. 

(1) What are the conspicuous properties of nitrous oxide f 

(2) What is the equation for I? (3) How could you dis¬ 
tinguish nitrous oxide from (a) the other oxides of nitrogen, 
(b) air, (c) oxygen, (d) hydrogen, (e) nitrogen, (/) carbon 
dioxide ? 

MOLECULAR WEIGHTS 

Exercise 41 — Weight of 22.4 Liters of Oxygen 

Materials. — Potassium chlorate, manganese dioxide, calcium 
chloride, glass wool or shredded asbestos. The potassium 
chlorate and manganese dioxide should be powdered and mixed in 
equal proportions, and then dried for an hour or more by heating 
in an oven to 110° C. 

Apparatus. — As in Fig. 53. A is a test tube attached to the 
bent tube F by a rubber stopper. B is a large bottle (2500 cc.) 
to be filled with water; it is provided with a two-hole rubber 
stopper, through which pass F and C, the latter being connected 
with a rubber tube C' to which is attached the short glass tube G. 
A Hofmann screw is attached to the rubber tube at the point E. 
Another bottle (2500 cc.) D serves to catch the water forced over 
from B through CC' by the oxygen generated in A. The hook 
S of aluminum wire permits A to be hung from the balance beam in 
weighing. Thermometer, barometer, balance, scales, weights. 

Note. — This exercise may be postponed until the pupil 
has acquired more experience in the laboratory. 

Object. — To find the weight of a certain volume of oxygen, 
reduce this volume to standard conditions, and calculate 
the weight of 1 liter of oxygen. ^ 

Copy the form of Record, as given below, in your labora¬ 
tory notes. Enter all weights and volumes in the proper 
place as soon as the weighing and measuring are done. 

Fill the space 1 in A with the dried mixture of equal weights 
of powdered manganese dioxide and powdered potassium 

82 


chlorate (Fig. 53). Push glass wool, or asbestos (the latter 
should be previously ignited to a red heat), into the space 2 
in A. Put small lumps of calcium chloride into 3 and glass 
wool into 4. Push the stopper well into the test tube. 
Wipe A with soft paper. Weigh AF accurately on the 
balance and enter the weight in the proper place in the 
Record. Weigh 

s 


the empty, dry, 



clean bottle D to ( 
a decigram on the 
scales, and enter 
the weight. 

Fill B with 
water nearly to 
the neck. Fill 
CC' with water 
and tighten the 
Hofmann screw E 
to prevent the 
Water from run- ^ IG ‘ — Apparatus for finding the weight of 22.4 
■ T , liters of oxygen 

nmg out. Insert 

F into the stopper of B. Push the stopper into the bottle, 
slowly at first, then hard; if water rises in F, loosen the 
screw at E slightly, remove A, and blow gently into F to 
force the water back into B. When properly adjusted, the 
water should be in B and CC' but not in F. Replace A, 
taking care not to crush the thin glass by pushing it too 
hard upon its stopper. Open the screw E. If the apparatus 
is tight, little or no water will flow out. It should be 
adjusted until air tight. Leave the screw E open. 

Heat A gently with a low flame, keeping the flame back of 
the space 2. The liberated oxygen will force the water from 
B into D. Heat A just hot enough to cause a gentle flow of 
water into D. When B is about half empty, stop heating. 
While A is cooling, stand a thermometer in D ; also read the 
barometer and enter the reading. When A is cold, raise B 
until the water is at the same level in B and D, pinch C f 
tight and remove it from D. Read and remove the ther¬ 
mometer, and enter the reading. 

83 















Dry D on the outside, if necessary, and then weigh it on 
the scales; enter the weight. The gain in weight (in grams) 
of D equals the volume of oxygen liberated (since 1 gm. of 
water = 1 cc.). 

Weigh AF on the balance ; enter the weight. Its loss in 
weight is the weight of the oxygen that passed into B. 


Record 


Weight of tube AF before heating. gm. 

Weight of tube AF after heating. gm. 

Weight of oxygen (W) . gm. 

Weight of bottle D and water. gm. 

Weight of bottle D empty. gm. 

Weight of water. gm. 

Volume of water. cc - 


Observed volume of oxygen (V') . . . . 

Temperature ( t ). 

Pressure read on barometer ( P') .... 
Pressure caused by water vapor (a) . . . . 

Corrected pressure. 

Corrected volume of dry oxygen (T) • • • 

Corrected volume of dry oxygen in liters (VI) 


Weight of 1 liter of oxygen. gm. 

Weight of 22.4 liters of oxygen. gm. 


Correct the observed volume (V') of oxygen for temper¬ 
ature ( t ), pressure (P'), and pressure of water vapor (a). 
That is, reduce the observed volume to the volume ( V ) it 
would occupy, if it were at 0° C., 760 mm., and in the dry 
state (i.e. free from water vapor). 

Water vapor exerts a pressure. Hence the pressure for 
which the observed volume ( V') must be corrected is the 
observed pressure (P r ) minus the pressure (a) due to the 
water vapor in the gas. The complete correction is made by 
this formula: — 


V = V' X 


273 


X 


P' - 


a 


273 + t 
84 


760 





















The values for a at different temperatures are given in the 
Appendix, § 1. 

Calculation of the weight of 1 liter of oxygen. Since 1 liter 
contains 1000 cubic centimeters, then V -f- 1000 is the 
actual volume of liberated oxygen expressed in liters (VI). 
The weight of liberated oxygen (W) is found by subtracting 
the weight of AF after heating from its weight before heating. 
The weight of 1 liter of oxygen in grams is found by dividing 
the weight of liberated oxygen by its volume, i.e. W -f* VI = 
the weight of 1 liter of oxygen. Multiply this weight by 22.4. 
Complete the entries in the Record in your laboratory notes. 


SULFUR 

*Exercise 42 — Different Forms of Sulfur 

Materials. — Roll sulfur, carbon disulfide. 

Apparatus. — Lens. 

I. Orthorhombic (or Rhombic) . —Put about 2 gm. of 
coarsely powdered roll sulfur in a test tube and add about 
5 cc. of carbon disulfide — remember to keep the carbon 
disulfide away from flames. Shake until most of the sulfur is 
dissolved, then pour some of the clear solution upon a glass 
plate to crystallize. Allow the liquid to evaporate; watch the 
crystallization. Examine the crystals with the eye and with 
a lens. Note the color, luster, and shape. Draw the best 
shaped one in your laboratory notes. 

II. Monoclinic. — Fix a folded filter paper firmly in a 
funnel, and place the funnel in a test tube which stands in a 
rack. Fill a test tube two-thirds full of roll sulfur, heat it at 
first throughout its length, and gradually increase the heat 
until all the sulfur is melted. Then quickly pour it upon the 
filter paper. Let it cool until crystals appear just below the 
surface, and then pour out the remaining melted sulfur at 
once into a dish of water. 

Remove the paper and adhering sulfur, and cut, or break, 
open the cone of crystallized sulfur. Observe the crystals, 
especially the shape, size, color, luster, and brittleness. Allow 

85 


the best crystals to remain undisturbed for a day or two; 
then examine again, and note any marked changes. 

III. Amorphous (or Plastic). — Put a few pieces of roll 
sulfur in a test tube. Heat carefully until the sulfur boils, 
and then quickly pour the molten sulfur into a dish of cold 
water. This is the plastic variety of amorphous sulfur. 
Note its properties. 

Preserve it and examine after twenty-four hours. Note 
its properties and compare them with those previously 
observed. 

Write in your laboratory notes a description of each kind of 
sulfur. 

*Exercise 43 — Preparation and Properties of Sulfur 
Dioxide (Short Method) 

Materials. — Sulfur, joss stick, litmus paper, potassium perman¬ 
ganate solution (dilute), bright colored paper. 

Apparatus. — Bottle fitted with cork. 

Caution. — Perform this experiment in the hood. 

I. Preparation. — Fill a deflagrating spoon with sulfur, set it 
afire, and lower the spoon into a bottle. In a minute or two, 
remove the spoon, and cover the bottle with a glass plate or 
(tightly) with a piece of filter paper. In the same way pre¬ 
pare and cover two more bottles of sulfur dioxide. 

II. Properties. — (a) Cautiously note the odor. After the 
smoke (which is not sulfur dioxide) has settled, note whether 
the gas has any color. Hold a blazing joss stick or a burning 
match in the bottle and note whether the gas burns or sup¬ 
ports combustion. 

(i b ) Stand the second bottle of gas mouth downward in a 
vessel of water (e.g. pneumatic trough). Shake vigorously, 
still keeping the mouth submerged. Observe the result. 
Slip a piece of filter paper under the mouth of the bottle, 
remove, invert, and test the liquid with litmus paper. Note 
the result. Save for (c). 

(c) Pour a few drops of very dilute potassium permanganate 
solution into the bottle saved from (b), and shake well. Com- 

86 


pare the color of the two liquids. If the result is not satisfac¬ 
tory, repeat, and use a bottle full of sulfur dioxide to which 
only 5 cc. of water has been added. 

(i d ) Moisten a piece of bright colored paper, put it in the 
third bottle of sulfur dioxide, and insert the cork. Observe 
any change in color. (If not decisive, try other kinds of 
paper.) 

Write answers to these questions in your laboratory notes. 
(1) What is the chemical equation for I? (2) What four 
'physical properties of sulfur dioxide are shown by II (a), (6)? 
(3) What chemical property by II (a)? (4) What acid was 

formed in II (b) ? (5) How would you explain the chemical 

change in II (c), (d)? 


Exercise 44 — Preparation and Properties of Sulfur Dioxide 
and Sulfurous Acid (Long Method) — Teacher’s Exercise 

Materials. — Sodium sulfite, dilute sulfuric acid, litmus paper, 
joss stick, colored flower, dilute potassium permanganate solu¬ 
tion and barium chloride solution. 

Apparatus. — As in Fig. 54. 

Caution. — Perform this exercise 
in the hood. 

I. Preparation. — (a) Sulfur 
Dioxide. — Put about 10 gm. of 
sodium sulfite in the flask, and in¬ 
sert the stopper with its tubes. 

Adjust the apparatus as shown in 
Fig. 54. Fill the cup with dilute 
sulfuric acid, press the pinch-clamp 
a little, and let the acid flow drop 
by drop upon the sodium sulfite. 

Sulfur dioxide is evolved and passes 
into the bottle, which should be 
removed when full, as previously 
described. Warm gently, if the 
action slackens. Moist blue litmus 
paper held for an instant at the mouth of the bottle will show 
(by change in color) when the latter is full. Collect two 

87 



Fig. 54. — Apparatus for pre¬ 
paring sulfur dioxide and 
sulfurous acid 














bottles of gas, cover each tightly with a piece of filter paper 
or a glass plate, and set aside until needed for II (a), etc. 

(b ) Sulfurous Acid. — As soon as the second bottle of gas 
has been removed and covered, put in its place a bottle one- 
fourth full of water. Adjust its height (if necessary) by 
wooden blocks, so that the end of the delivery tube is just 
above the surface of the water. Continue to add the acid and 
to heat at intervals. Shake the bottle occasionally. When 
II (a), etc., have been done, proceed with this solution as 
in III (a), etc. 

II. Properties of Sulfur Dioxide Gas. — Proceed as in 
Exercise 43 II (a), ( b ), (c), ( d ). 

III. Properties of Sulfurous Acid. — (a) Observe the odor 
and the taste cautiously. 

(b) Apply the litmus test, and note the result. 

(c) Drop a short piece of magnesium ribbon into 10 cc. of 
the solution. Warm slightly, if there is no action. Note the 
liberation of a gas. 

( d ) Add a few drops of dilute potassium permanganate solu¬ 
tion to 5 cc. of sulfurous acid and shake. Observe the result. 

(e) Optional. Put about 10 cc. of sulfurous acid in an 
evaporating dish, support the dish on a gauze-covered ring 
attached to an iron stand, heat in the hood, and note the odor 
of tile liberated gas. Blow the gas out of the dish frequently, 
and then smell of the liquid. Boil until most of the liquid is 
evaporated, and test the remainder with litmus paper. Note 
the final effect of heat on sulfurous acid. 

(/) Optional. ; Put 10 cc. of sulfurous acid into a test tube, 
cover loosely, and let it stand exposed to the air for a day or 
two Add 10 cc. of water, boil for a minute or two, and test 
the Solution for S0 4 -ions by adding a few drops of barium 
chloride solution. Note the result. 

(i g ) Put 10 cc. of sulfurous acid in a test tube, add 2 cc. of 
concentrated nitric acid, and boil carefully for a minute or 
two. Add about 10 cc. of water, shake, and test for sulfate 
ions, as in (/). Note the result. 

Write a brief account of I in your laboratory notes. 

Write also answers to the questions at the end of Exercise 43. 

88 


Write also answers to these questions. (1) What is the 
chemical equation for I (a) ? (2) For I (6) ? (3) What do 

III (a) and ( e ) show about the stability of sulfurous acidf 
(4) How would you explain III (d), (/), ( g ) in terms of oxida¬ 
tion and reduction? (5) Is the test for SOrions in III (/), (<?) 
positive or negative ? Explain. 


^Exercise 45 — Properties of Sulfuric Acid 

Materials. — Concentrated sulfuric acid, thin stick of wood, sugar. 
Apparatus. — Graduated cylinder (100 cc.) and hydrometer for 

heavy liquids (optional). 

Caution. — Concentrated sulfuric acid is a corrosive liquid. 
Do not spill it on the flesh or clothing. 

(a) Weigh (on the scales) a 25 cc. graduated cylinder, pour 
in concentrated sulfuric acid to a convenient height (e.g. 
20 cc.), and weigh again. Read the exact 
volume of the acid. From the weight and 
volume of the acid, calculate its specific 
gravity by dividing the weight (in grams) by 
the volume (in cubic centimeters). Copy 
this form in your laboratory notes and com¬ 
plete the calculation: — 

x = Vol. of acid = cc. 

y = Wt. of acid = gm. 

Specific gravity = y -r- x = . Ans. 

( b ) Optional. Find the specific gravity of 
a sample of the same acid by reading the 
hydrometer which floats in the acid (Fig. 55). 

(This apparatus should be arranged for the 
class by the Teacher.) Compare with the 
result in (a). 

( c ) Care. Stand a test tube in the rack. 

Add 10 cc. of water. Pour 10 cc. of con¬ 
centrated sulfuric acid into a graduated cylinder and then 
slowly add the acid to the water. Stir with a glass rod, 
and observe at once the change in temperature by touching 
the tube with the hand. Save the solution for (d) and (e)> 

89 


Fig. 55. — Find¬ 
ing the specific 
gravity of sul¬ 
furic acid with 
the hydrometer 





(i d ) Dip a glass rod into the sulfuric acid from (c) and write 
some letters or figures on a sheet of paper. Move the paper 
back and forth slowly above a low flame, taking care not to set 
fire to the paper. As the water evaporates, the dilute acid 
becomes concentrated. Observe the effect on the paper. 
(Paper is largely a compound of carbon, hydrogen, and 
oxygen, and the hydrogen and oxygen are present in the pro¬ 
portion to form water.) 

(e) Warm the acid in the test tube saved from (c), stand a 
stick of wood in the acid, and allow it to remain for fifteen 
minutes or more. Then remove the stick and wash off the 
acid. Note the change in the wood. 

(/) Put 5 gm. of sugar in an evaporating dish, add just 
enough warm water to make a thick sirup, stir, and stand the 
dish on a block of wood (or in the sink). Cautiously pour 5 
or 10 cc. of concentrated sulfuric acid upon the liquid. Stand 
back and observe the result. 

Write answers to these questions in your laboratory notes. 

(1) What is the specific gravity of the sample of concentrated 
sulfuric acid you usedf (2) How would you interpret the 
conspicuous result in ( d ), (e), (/)? (3) What does ( c ) show 
about the thermal effect of mixing sulfuric acid and water f 

^Exercise 46 — Tests for Sulfuric Acid, Sulfates, 
and SO 4-ions 

Materials. — Sulfuric acid, sodium sulfate, barium chloride solu¬ 
tion. 

(а) Sulfuric Acid. Devise a test for (1) concentrated and 

(2) dilute sulfuric acid from Exercise 45. 

(б) Sulfuric Acid and Soluble Sulfates, i.e. solutions con¬ 
taining S0 4 -ions. — Add barium chloride solution to the 
solution of the acid or the sulfate. If a fine, white insoluble 
precipitate (barium sulfate) is formed, the original solution 
contained S0 4 -ions. 

Note. — To test for an insoluble sulfate, such as barium or 
calcium sulfate, proceed as in Exercise 53 B (6). 

Write in your laboratory notes the test devised for ( a ) and the 
statement of the test for SO 4-ions, including the ionic equation. 

90 


^Exercise 47 — Preparation and Properties of Hydrogen 
Sulfide (Short Method) 

Materials. — Ferrous sulfide, dilute hydrochloric acid, lead 
nitrate solution. 

Apparatus. — As in Fig. 56 for ( d ). 

Caution. — Hydrogen sulfide is a poisonous gas and has an 
offensive odor. It should not be inhaled nor allowed to 
escape into the laboratory. All exercises with hydrogen 
sulfide should be performed in the hood. 

(a) Slip a lump of ferrous sulfide carefully into a test tube, 
stand the tube in the rack, add 5 cc. of dilute hydrochloric 
acid, and cautiously note the odor of the gas. 

( b ) Wet a piece of filter paper with lead nitrate solution 
and hold it in the escaping gas. Note the 
change in color. 

(c) If necessary, add a little more ferrous 
sulfide and dilute hydrochloric acid to the 
test tube, and make two tests. (1) Hold 
a lighted match at the mouth of the tube. 

Observe the flame and its color. Cautiously 
note the odor of the gaseous product. 

(2) Lower a cold dish down upon the flame 
and note the deposit on the dish. 

(i d ) Arrange an apparatus as in Fig. 56. 

Fill B half full of water. Put ferrous sul¬ 
fide and dilute hydrochloric acid in the 
test tube A and let the gas bubble through 
the water in the test tube B for a few minutes. Use the 
solution in Supplementary Exercise 38. Cork tightly, unless 
it is to be used soon. 

Write answers to these questions in your laboratory notes. 

(1) How would you describe the odor of hydrogen sulfide? 

(2) What lead compound was formed in (b) ? What is the 

chemical equation? (3) What compounds are formed by the 

ordinary combustion of hydrogen sulfide? What is the equa¬ 
tion ? (4) What is the effect of cooling a hydrogen sulfide flame ? 

(5) Does hydrogen sulfide dissolve in water ? 

91 



Fig. 56. — Appara¬ 
tus for preparing 
hydrogen sulfide 
water 









SUPPLEMENTARY EXERCISES ON SULFIDES 


Supplementary Exercise 37 — Preparation and Properties 
of Hydrogen Sulfide — Teacher’s Exercise 

Materials. — Ferrous sulfide, dilute hydrochloric acid, lead 
nitrate solution. 

Apparatus. — As in Fig. 57; stoppered bottle. (The apparatus 
shown in Fig. 14 may be used if the lower end of the thistle tube 
is kept below the surface of the acid.) 

Caution. — Hydrogen sulfide is a poisonous gas and has an 
offensive odor. It should not be inhaled nor allowed to 
escape into the laboratory. All exercises with hydrogen 
sulfide should be performed in the hood. 

I. Preparation. — Construct and arrange the apparatus 
as shown in Fig. 57. Put 10 gm. of coarsely powdered 
ferrous sulfide in the bottle A, insert the stopper tightly, and 
adjust the apparatus so that the end of the delivery 
0 tube will be under the support of the pneumatic 
trough. Introduce a little dilute hydrochloric acid 

through the dropping 
tube. Hydrogen sul¬ 
fide is rapidly evolved. 
If the evolution of 
gas slackens or stops, 
add more hydro¬ 
chloric acid. Collect 
three bottles, remov¬ 
ing each as soon as 
full and covering 
tightly with a piece 
Set aside until needed. When all the 
proceed at once with II. 



Fig. 57. — Apparatus for preparing hydrogen 
sulfide 


of dry filter paper, 
bottles have been filled with gas, 

II. Properties. — (a) Waft a very little of the gas cau¬ 
tiously toward the nose, and note the odor. This odor is 
characteristic of hydrogen sulfide, and is a decisive test. 

(b) Test the gas from the same bottle with (1) both kinds of 
moist litmus paper, and note if hydrogen sulfide is acid, 
alkaline, or neutral, and (2) a piece of filter paper wet with lead 
nitrate solution, and note the change in color. 

92 

















(c) Hold a lighted match at the mouth of the same bottle. 
Observe the color of the flame. Note very cautiously the odor 
of the gaseous product. 

( d ) Burn another bottle of hydrogen sulfide and hold a 
cold, dry dish in the burning gas. Note the deposit on the 
dish. 

(e) Pour several drops of concentrated nitric acid into a 
bottle of hydrogen sulfide, cover, and shake. Note the solid 
product. 

Write answers in your laboratory notes to the questions at the 

end of Exercise 47. 

Write also answers to these questions. (6) What is the chem¬ 
ical equation for the reaction in I? (7) What are two tests for 
hydrogen sulfide f (8) How would you explain the result in 
II (6)? 

Optional Exercises 

1. Summarize briefly the properties of hydrogen sulfide. 

2. State the experimental evidence of its composition. 

Supplementary Exercise 38 — Preparation and Properties 
of Sulfides — Teacher’s Exercise 

Materials. — Hydrogen sulfide water, clean copper wire, bright 
silver coin, lead oxide (litharge); solutions of tartar emetic, zinc 
sulfate, cadmium nitrate, and silver nitrate; sulfur (powdered) 
and iron thread (or clean filings) for (d ). 

(а) Put 10 cc. of hydrogen sulfide water in a test tube and 
slip in a piece of clean copper wire and a bright silver coin. 
Note the result in each case after several minutes. The 
products are sulfides of the respective metals. 

(б) Put a little litharge — the brownish yellow oxide of 
lead — in a test tube, cover it with hydrogen sulfide water, 
and warm gently. The product is lead sulfide. Note its 
color. 

(c) Add to separate test tubes a few cubic centimeters of 
solutions of (1) tartar emetic (a compound of the metal 
antimony), (2) zinc sulfate, (3) cadmium nitrate, and 

93 


(4) silver nitrate. Add 5 cc. of hydrogen sulfide water to the 
solutions. Note the color of each product. 

(d) Mix thoroughly on a piece of paper about 3 gm. of 
powdered sulfur and 5 gm. of clean iron filings. Slip the 
mixture into a test tube and heat intensely. Remove the 
test tube from the flame as soon as action begins. Remove 
the product by breaking the end of the test tube, add a little 
dilute hydrochloric acid to it, and note the result. 

Write answers to these questions in your laboratory notes. 
(1) What is the name, formula, and color of the sulfides formed 
in (a), ( b ), (c)? (2) What are the chemical equations for the 

reactions in (c) (2), (3), (4) ? (3) What are the corresponding 

ionic equations f (4) What is the name and formula of the 
sulfide formed in (d) ? (5) What is a test for sulfide ionf 

CARBON — FLAME 

^Exercise 48 — Destructive Distillation of Soft Coal 
and Examination of the Products 

Materials. — Soft coal, litmus paper, lead nitrate solution. 
Apparatus. — As in Fig. 58. 

I. Distillation. — Fill the large “test tube two-thirds full of 
coarsely powdered soft coal, insert the stopper with its open 
delivery tube, and clamp the test tube 
to the iron stand as shown in Fig. 58. 
Heat the whole tube gently at first, 
gradually increase the heat, and finally 
heat intensely the part containing the 
coal. 

II. Examination of the Products. — 

(a) As soon as the gas begins to escape, 
lay a piece of wet red litmus paper on 
the end of the tube and continue to heat 
intensely; wet the paper, if it dries. 
Observe any change in the color of 
the litmus paper. Remove the paper. 

(b) Hold at the end of the tube a piece of filter paper which 
has been moistened with lead nitrate solution; observe the 

94 



Fig. 58. — Apparatus for 
distilling coal 












effect of the gas on the paper. The discoloration is caused by 
lead sulfide which is produced by the interaction of lead 
nitrate and the sulfides in the liberated gas. 

(c) Heat intensely, and light the gas at the end of the tube. 
Observe the flame, especially the color. 

(d) Discontinue heating, let the apparatus cool somewhat, 
disconnect, and break open the test tube. Examine the 
contents, and note the properties of the solid and liquid 
products. 

Write a brief account of this exercise in your laboratory notes. 

* Exercise 49 — Distillation of Wood — Teacher’s Exercise 

Materials. — Chips of wood, litmus paper. 

Apparatus. — As in Fig. 59. 

Construct and arrange an apparatus as in Fig. 59. Fill the 
test tube A half full of chips of wood. Fill the bottle D half 
full of cold water. The test n 

tube C, which serves as a con¬ 
denser, is empty. The exit ^ 



tube E is drawn out to form a C 


small jet at the outer end. 
Adjust finally so that the lower 
end of the tube B is about 
2.5 cm. (1 in.) from the bottom 
of the condenser tube C. 



Heat the test tube A gently 
at first and then strongly where 
the wood is placed. Note 
the result in both test tubes 


(A and C). ^ ^ 

Continue to heat, and bring Fig - 59 * — Ap ^^ us for dlstlllmg 
the flame to the end of the jet 

tube E. Note the result. If no result, heat strongly and 
try again. 

When the distillation causes no more change in the test tube 
A, stop heating, let the apparatus cool, and disconnect the 
two test tubes. 


95 




















(a) Examine the contents of A and note its properties. 
Note also the conspicuous difference from the original wood. 

( b ) Note the contents of the test tube C. Smell, and note 
the odor. Test with blue litmus paper and note the effect. 

Write a brief description of this exercise in your laboratory 
notes. Write also answers to these questions. (1) What is the 
name of the residue in A ? (2) Of the dark liquid in C f 

(3) What is one substance in C according to the litmus test f 


^Exercise 50 — Illuminating Gas Flame — 
Teacher’s Exercise 

Material. — Calcium hydroxide solution. 

Apparatus. — Gas burner (Fig. 60) or tip, glass tube. 

( a ) Examine a gas burner tip, noting especially the slit. 

(b) If an ordinary gas burner is not available, attach the 
tip to a rubber tube and slip the tube over the top (or 

just inside) of a Bunsen burner. Light 
the gas. Note the yellow and black 
parts (Fig. 60). 

Turn off the gas slowly until the 
flame is very small and note the change 
in the size of the parts, and finally the 
black and the blue parts. 

Turn on the gas slowly and note the 
change in the size of the parts. 

(c) Hold a glass tube in the upper 
part of the yellow flame. Note the 
deposit on the tube, and conclude 
(1) what it is and (2) where it came 
from. Lower the flame and hold a 
cold, dry bottle low down almost upon 
the flame. Note if a deposit is formed. If so, conclude 
what it is and why it was formed. 

(d) Hold a cold, dry bottle mouth downward just over the 
flame. Note the deposit inside the bottle. Pour about 10 cc. 
of calcium hydroxide solution into the bottle, and shake. 

96 



Fig. 60. — Gas burner and 
flame 





Note the result. Conclude what are the two products of the 
combustion of illuminating gas. 

Write a brief account of this exercise in your laboratory notes, 
recording all observations and conclusions under the lettered and 
numbered parts. 


^Exercise 51 — Candle Flame — Teacher’s Exercise 


Materials. — Candle, piece of stiff paper, calcium hydroxide solu¬ 
tion, lead pencil, copper wire (15 cm. or 6 in. long). 

Stick a short candle to a block of wood by means of a little 
melted candle wax. 

(а) Hold a cold, dry bottle over the lighted candle. Note 
the product seen inside the bottle. 

Remove the bottle, pour in a little calcium hydroxide 
solution, and shake. Note the result. Conclude what are 
the two main products of a burning candle. 

(б) Blow out the candle flame, and immediately hold a 
lighted match in the escaping smoke. Note if the candle 
relights. Conclude (1) what is the general nature of this 
smoke, and (2) how it is related to the candle wax. 

(c) Press a piece of stiff paper carefully for an instant down 
upon the steady candle flame almost to the wick. Repeat 
several times with different 
parts of the paper. Note the 
result. Conclude what the 
marks on the paper show about 
the structure of the flame. 

(d) Roll one end of the 
copper wire around a lead 
pencil to form a spiral about 
2 cm. (or 1 in.) long. Press 

the spiral down slowly upon the candle flame (Fig 
Note the result. Cool the wire and repeat 
an explanation of the result. 

Write a brief account of this exercise in your notes, recording 
the observations and conclusions under the lettered and num¬ 
bered parts. 



Fig. 61.- 


Effect of cooling a candle 
flame 

61). 

Decide upon 


97 








Optional Exercises 

1. Draw a candle flame, showing the parts. 

2. Is there any essential difference between a candle and 
a gas or a lamp flame ? 

3. Why do candles and lamps often smoke ? 


^Exercise 52 — Bunsen Burner and Bunsen Burner 
Flame — Teacher’s Exercise 

Materials. — Powdered wood charcoal, pin, copper wire, 

tube. 

(a) Optional. Take apart a Bunsen burner and study the 
construction. Note the essential parts. 

( b ) Close the holes at the bottom of a lighted burner and 
hold a glass tube in the upper part of the yellow flame. Note 
the deposit. Conclude (1) what it is and (2) where it came 
from. 

Open the holes and move* the tube up and down in the 
colorless Bunsen flame. Note the effect on the deposit. 

(c) Dip a glass tube a short distance into some powdered 
wood charcoal, place the end containing, the charcoal in one 
of the holes at the bottom of the lighted burner, and blow 
gently two or three times into the other end. Note the 
result. Decide upon an explanation. 

(i d ) Open and close the holes of a lighted burner several 
times. Note the result. Pinch the rubber tube to extin¬ 
guish the flame, then light the gas at the holes. Note the 
change produced in the*flame. Conclude 
what is the object of the holes. 

(e) (1) Lay a match across the top of 
the tube of a lighted Bunsen burner. When 
the match begins to burn, remove and ex¬ 
tinguish it. Note where it is charred. 

(2) Press a piece of wire gauze down 
upon the flame. Note the appearance of 
the gauze (Fig. 62). 

(3) Stick a pin through a match near the head, and suspend 
it across the burner as in Fig. 63. Turn the gas on full and 

98 


Fig. 62. — Studying 
the cones of a 
Bunsen flame 




Fig. 63. — Studying 
the lower part of 
a Bunsen flame 


light it. Note the effect, if any, on the match. Conclude 
what the whole of ( e ) shows about the structure of the lower 
part of the Bunsen flame. Verify your 
conclusion, if necessary, by (/). 

(/) Hold one end of a glass tube (about 
15 cm. or 6 in. long) in the Bunsen flame 
about 2 cm. (1 in.) from the top of the 
burner tube (Fig. 64). 

Hold a lighted match 
for an instant at the 
upper end of the tube; 
raise or lower the tube 
slightly (still keeping 
the end in the flame) and observe the re¬ 
sult. Conclude (1) what the result shows 
about the structure of the Bunsen flame, 
and (2) how it verifies ( e ). 

(g) Find the hottest part of the flame, 
when a full current of gas is burning, by 
moving a copper wire up and down in the flame. Measure 
its distance, approximately, from the top of the burner tube. 
Enter the result in your laboratory notes by a sketch which 
shows the whole flame and the location of the hottest part. 

( h ) Optional. Examine an imperfect Bunsen burner flame 
— one which shows the outlines of the inner part. Note the 
general shape of each main part. Draw a vertical and a cross 
section in your laboratory notes. 

(i) Optional. Using the same burner as in (h), lower the 
flame gradually until it strikes back. Note (1) the odor and 
(2) the location of the flame. 


Fig. 64. — Studying 
the inner cone of 
a Bunsen flame 


Write a brief account of this exercise in your laboratory notes, 
including under lettered and numbered parts the observations, 
conclusions, and sketches. 


Optional Exercises 

1. Sketch the essential parts of a Bunsen burner. 

2. Examine and describe a gas range burner. 

3. As in 2, a gas range burner flame. Compare it with 
a typical Bunsen flame. 


99 








^Exercise 53 — Reduction and Oxidation with the Blowpipe 

Materials. — Charcoal, lead oxide, sodium carbonate, calcium 
sulfate, powdered wood charcoal, silver coin, zinc. 

Apparatus. — Blowpipe, blowpipe tube. 

A. Using the Blowpipe. — Slip the blowpipe tube (Fig. 65) 
into the burner tube. Light the gas and lower the flame until 

it is about 4 cm. (1.5 in.) high. Rest the tip of 
the blowpipe (Fig. 66) on the top of the blowpipe 
tube, placing the tip just within the flame. Put 
the other end of the blowpipe between the lips, 
puff out the cheeks, inhale through the nose, and 
exhale into the blowpipe, using the cheeks some¬ 
what as bellows. Do not blow in puffs, but pro¬ 
duce a continuous flow of air through the blowpipe 
(Fig. 67). The flame should be an inner blue cone 
surrounded by an outer and almost 
invisible cone (Fig. 68). 

B. Reduction. — (a) Make a cavity 
in one end of the flat side of a piece 
of charcoal. Fill it with a mixture of 


y 

Fig. 65.— 
Blowpipe 
tube 


r 


Fig. 66. — Blowpipe 



Fig. 67. — Using the 
blowpipe 


equal parts of sodium carbonate and 
lead oxide, and heat the mixture in 
the reducing flame (B in Fig. 68). In 
a short time bright, silvery globules 
should appear on the charcoal. Let 

the mass cool, and pick out the largest 
globules. Put one or two in a mortar, 
and strike with a pestle. Note if they are 
soft or hard, malleable or brittle. Con¬ 
clude (1) whether the metal is lead and 
(2) if so, what became of the oxygen. 

(i b ) Grind together in a mortar a little calcium sulfate and 
powdered wood charcoal, adding just enough water to hold 
the mass together. Heat some of this paste in the reducing 

100 


Fig. 68. — Blowpipe 
flame — A oxidizing 
and B reducing 








flame as in (a). Scrape the mass into a test tube, boil in a 
little water, and put a drop of the solution on a clean silver 
coin. Note the result. If a dark brown stain is produced, it 
is evidence of the formation of silver sulfide. Repeat, if no 
such stain is produced. The silver sulfide is formed by the 
interaction of the silver and calcium sulfide. Conclude how 
this exercise illustrates reduction. 

C. Oxidation. — Heat a small piece of zinc on charcoal in 
the oxidizing flame (A in Fig. 68). Direct the flame across 
the zinc so that most of the product will form a coating on the 
charcoal. Observe the color of the coating on the charcoal 
when both hot and cold. 

Write a brief account of this exercise in your laboratory notes. 

Write also the name and formula of each obvious product of 
the reduction and oxidation. 


SUPPLEMENTARY EXERCISES ON CARBON 
AND FLAME 


Supplementary Exercise 39 — Carbonic Acid — 
Teacher’s Exercise 

Materials. — Marble; solutions of sodium hydroxide and phenol- 
phthalein. 

Apparatus. — Carbon dioxide gen¬ 
erator with washing tube. 


Construct and arrange a car¬ 
bon dioxide generator like that 
shown in Fig. 69. (A bottle 
may be used in place of the test 
tube A.) Put marble chips in A 
and water in B (to wash the 
acid from the gas.) Use dilute 
hydrochloric acid. Fill the bottle 
C half full of water, add a few 

drops of phenolphthalein solution, and just enough sodium 
hydroxide solution to color the liquid a faint pink (after 
shaking). 



Fig. 69. — Apparatus for prepar¬ 
ing and washing carbon dioxide 


101 





















Pass a slow current of carbon dioxide through the liquid in 
the bottle C until a definite change is produced in the absorb¬ 
ing liquid. Note the result. Compare the final with the 
original liquid in C. 

Write a brief account of this exercise in your laboratory notes, 
including equations for the essential chemical change in A and 
in C. 


Supplementary Exercise 40 — Acetylene — 
Teacher’s Exercise 


Materials. — Calcium carbide, dilute potassium permanganate 
solution. 

Apparatus. — As in Fig. 70, three bottles. 


Caution. Acetylene mixed with air explodes. Perform 
this exercise with great care. 

I. Preparation. — Arrange the apparatus as in 
Fig. 70. Put about 5 gm. of calcium carbide in the 
bottle A. Fill the cup of the dropping tube with 

water, and let water 
drop very slowly into 
the bottle. Acety¬ 
lene will be given off. 
Collect the gas over 
water as usual. Re¬ 
ject the first bottle. 
Collect two bottles of 
acetylene. Collect a 
third bottle of a mix¬ 



Fig. 70. — Apparatus for preparing acetylene 


ture of air and acetylene thus: Fill the bottle at first only 
about half full of water, invert, and let the acetylene fill the 
bottle; set this bottle apart from the others. 

II. Properties. — (a) Drop a lighted match into a bottle 
of acetylene. Observe the flame, especially the color, lu¬ 
minosity, and smokiness. 

(b) To another bottle of acetylene add 5 cc. of dilute 
potassium permanganate solution, shake well, and observe the 
result. 


102 














(d) Drop a lighted match cautiously into the bottle con¬ 
taining the mixture of acetylene and air. Note the result. 

Write a brief account of this exercise in your laboratory notes, 
including the equations for I, II (a), a summary of II, and an 
explanation of II ( b ). 


ORGANIC COMPOUNDS 

Exercise 54 — Sugars (Sucrose (Cane Sugar) and 
Dextrose) 

Materials. — Cane sugar, glucose, sodium hydroxide and Fehling’s 

solution; (optional) substances enumerated in (c). 

(a) Add 10 cc. of Fehling’s solution (see Appendix, § 13, 
List G) to 5 cc. of dextrose solution, and heat to the boiling 
point. Note the precipitate. It is cuprous oxide. Note 
especially the color. 

(b) Repeat (a), using sucrose (cane sugar) solution instead 
of glucose. Heat, but do not boil the mixed solutions. Note 
the result. Compare with (a). 

(c) Optional. Apply Fehling’s test for dextrose (and 
similar sugars) to cheap candy, maple sugar, molasses, table 
sirups, jelly, jam, fruits. Prepare and use clear solutions. 
Note each result. 

(d) Put 10 cc. of sucrose solution in an evaporating dish, 
add 1 cc. of concentrated hydrochloric acid, and boil about 
ten minutes. Neutralize with sodium hydroxide solution 
(mix well), and test with Fehling’s solution. Note the 
result. 

Write answers to these questions in your laboratory notes. 
(1) What is a test for glucosef (2) How can sucrose be 
distinguished from glucose? (3) Optional. What does (c) 

show about the distribution of glucose? (4) How does (d) 

illustrate hydrolysis and inversion f (5) What is the formula 
of cuprous oxide f 


103 


Exercise 55 — Properties of Starch 

Materials. — Starch, Fehling’s solution, dilute iodine solution. 

Prepare a starch mixture by boiling about i gm. of pow¬ 
dered starch for a few minutes in 50 cc. of water; stir or 
agitate the mixture during the boiling. Make these tests 
with the starch mixture. 

(a) (1) Pour half of it into an evaporating dish which 
stands on a gauze-covered ring, add 2 cc. of concentrated 
hydrochloric acid, mix well, and boil gently for ten minutes; 
add water occasionally to replace that lost by evaporation. 
Meanwhile proceed with (6). 

(2) As soon as the mixture in (1) has been boiled ten 
minutes, take out a little, add sodium hydroxide solution to 
alkaline reaction (shake well), and apply Fehling’s test. Note 
the result. Continue the heating for ten or more minutes, 
and test again. Note the final result. Compare with (6). 

( b ) To 10 cc. of the original starch mixture add 10 cc. of 
Fehling’s solution, shake, and warm. Observe the result. 
Save for comparison with (a). 

(c) Add a drop or two of very dilute iodine solution to the 
rest of the starch mixture. Observe the color. (This test 
for starch is delicate, and dilute mixtures should be used.) 

(d) Test potato, rice, and bread for starch by moistening 
each separately with water, and then adding a drop or two of 
very dilute iodine solution. Note the result in each case. 

Write answers to these questions in your laboratory notes. 
(1) What is the result of boiling starch with acid ? (2) Does 

starch react with Fehling’s solution? (3) What effect does 

iodine have on starch f 

Exercise 56 — Testing Baking Powders 

Materials. —Baking powder (tartrate, phosphate, alum), 

vinegar, sour milk, lemon juice, solutions of calcium hydroxide, 

iodine, silver nitrate, ammonium chloride, sodium hydroxide, 

ammonium molybdate and ammonium oxalate. 

Note. — Different varieties of baking powder may be 
tested by individuals or sections, and the results compared. 

104 


(а) Carbonates. — (1) Put a little baking powder in a test 
tube, add a few drops of dilute hydrochloric acid, and test the 
escaping gas for carbon dioxide with a tube which has been 
dipped into calcium hydroxide solution (Fig. 71). Note the 
result. 

(2) Put 2 gm. of baking powder in a test tube, add 15 to 
20 cc. of water, and shake well. Let the action continue a 
short time, and then test the solution 
as in (1). Note the result. 

(3) Add sour substances, e.g. vine¬ 
gar, sour milk, lemon juice, separately 
to a little baking powder, and note 
the result. 

(б) Starch. — Apply the iodine test 
for starch to a little baking powder 
mixed with water. Note the result. 

(c) Tartrates. — Prepare a cold solu¬ 
tion of baking powder by shaking 
about 10 gm. of the substance with 
50 cc. of water and stirring until all the 
gas is liberated. (It is better to boil 
it, and then cool it for use.) Filter, if not clear, and use the 
clear solution in this and succeeding tests. 

(1) Clean a test tube by boiling sodium hydroxide solution 
in it and then washing thoroughly with water. Put 10 cc. of 
silver nitrate solution in the cleaned test tube, and add 
ammonium hydroxide slowly until the precipitate at first 
formed redissolves, taking care to mix the solutions. Add 
10 cc. of the baking powder solution and warm gently. 
Tartrates, if present, will reduce the silver compound to silver, 
which will coat the inside of the test tube. 

(2) Put about 5 cc. of the prepared solution in an evapo¬ 
rating dish, add a few drops of concentrated sulfuric acid, 
and heat gently. Tartrates, if present, will char and smell 
like burnt sugar. 

(d) Sulfates. — To 5 cc. of the baking powder solution 
(prepared as above) add dilute hydrochloric acid to acid 
reaction and boil (to remove any carbon dioxide); then test 
with barium chloride solution. Note the result. 

105 



Fig. 71. — Testing for 
carbon dioxide 








(e) Phosphates. — Warm 5 cc. of the baking powder 
solution, acidify with concentrated nitric acid, and add 5 
cc. of ammonium molybdate solution. A yellow precipitate 
indicates phosphates. Note the result. 

(/) Ammonium salts. — Boil 5 cc. of the baking powder 
solution with an equal volume of sodium hydroxide solution. 
The presence of ammonium salts is shown by the liberation of 
ammonia gas, which can be detected by its odor. Note the 
result. 

(g) Aluminum salts. — Boil 5 cc. of the baking powder 
solution with 1 or 2 cc. of dilute hydrochloric acid, filter if not 
clear, and add 10 cc. (or more) of ammonium chloride and 
10 cc. of ammonium hydroxide to the filtrate. A whitish 
flocculent precipitate (aluminum hydroxide) indicates alumi¬ 
num salts. Note the result. 

(h ) Calcium salts. — Boil 10 cc. of the baking powder 
solution with dilute hydrochloric acid (to remove any carbon 
dioxide), add ammonium hydroxide to alkaline reaction 
(stir, and test with litmus paper), filter, if not clear, and 
then add ammonium oxalate solution. Calcium compounds 
produce a white precipitate (calcium oxalate). Note the 
result. 

Write the results of these tests in tabular form in your 
laboratory notes. 

SUPPLEMENTARY EXERCISES ON ORGANIC 
COMPOUNDS 

Supplementary Exercise 41 — Esters 

Materials. — Acetic acid, ethyl alcohol, calcium butyrate, meth¬ 
anol, salicylic acid. 

(а) Cautiously add 3 or 4 drops of concentrated sulfuric 
acid to a mixture of 5 cc. each of acetic acid and ethyl alcohol. 
Shake the mixture and warm gently. Note the odor. It is 
due to the ester called ethyl acetate. 

(б) Put a very little calcium butyrate in a test tube, add 
2 or 3 cc. of water, the same volume of ethyl alcohol, and 3 

106 


or 4 drops of concentrated sulfuric acid. Shake well, and 
warm gently. The ester produced is ethyl butyrate. Note 
the odor. 

(c) Proceed as in (6), using salicylic acid, methanol, water, 
and concentrated sulfuric acid. The ester is methyl salicyl¬ 
ate. Note the odor. 

Write a brief account of this exercise in your laboratory notes. 
In your notes write this equation in complete form: 

-+-= CH3COOC2H5 +- 

Ethyl Acetic Ethyl Water 

Alcohol Acid Acetate 

% 

Supplementary Exercise 42 — Soap 

Materials. — Sodium hydroxide, lard, soap, phenolphthalein, and 

(saturated) salt solution. 

I. Preparation. — ( a ) Dissolve 10 gm. of sodium hy¬ 
droxide in 75 cc. of water, add 30 gm. of lard, and boil the 
mixture in a porcelain (or metal) dish for an hour or more ; 
add water occasionally to replace that lost by evaporation. 
Then add about 50 cc. of a saturated salt solution. Stir con¬ 
stantly during the addition of the solution. Let the mass 
cool, and remove the cake of soap. 

(6) Optional. Prepare soap by the method given on a can 
of commercial “ lye.” 

II. Properties. — (a) Leave soap shavings exposed to the 
air for several days. Note the result. 

( b ) (1) Test the soap made in I with wet litmus paper. 
Note the result. Test other samples and compare. 

(2) Put a few drops of phenolphthalein solution (alcoholic) 
on samples of dry soap. Note the results. This is a test for 
“ free alkali.” 

(c) Prepare 25 cc. of a solution of the soap made in I (a). 
Warm it and examine the surface for fat (film or globules). 
Note the result. 

(d) Add 20 cc. of dilute sulfuric acid to 10 cc. of soap 
solution. Note the result. The precipitate is a mixture of 
palmitic and stearic acids. 


107 





Write a brief account of I in your laboratory notes. 

Write also answers to these questions. (1) What does II (a) 
show about water in soap ? (2) What does II ( b ) show about 
alkali in soap f (3) If as fat detected in II (c) ? Why f 

Optional Exercises 

1. Complete this equation : 

C 3 H 6 (Ci 7 H 35 COO) 3 +-= C 17 H 35 COONa + C 3 H 5 (OH) 3 

Fat Alkali Soap (Sodium Glycerin 

(Glyceryl Stearate) (Sodium Hydroxide) Stearate) (Glyceryl Hydroxide) 

2. Complete this equation: 

C 17 H 35 COONa + H 2 S0 4 = Ci 7 H 36 CDOH +- 


Supplementary Exercise 43 — Testing for Nutrients in Food 
— Teacher’s Exercise 

Materials. — Foods; Molisch’s, iodine, Fehling’s, and sodium 
hydroxide solutions; gasolene, concentrated nitric acid, very 
dilute copper sulfate solution. 

Apply tests for carbohydrate, fat, and protein to various 
foods. 

I. Carbohydrate. — (a) Apply the Molisch test. To 5 cc. 
of a clear dilute solution of the carbohydrate (or food), add 
2 cc. of Molisch’s solution, and shake. Incline the test tube 
and carefully pour down the inside 5 cc. of concentrated 
sulfuric acid so that two layers will form. At the contact 
zone a red-violet color will appear slowly. Note the result. 

(b) Apply the iodine test for starch (Exercise 55) and 
Fehling’s test for sugar (Exercise 54). Note each result. 

II. Fat. — Grind the sample with gasolene (Care!) in a 
mortar, pour off the gasolene into an evaporating dish, let it 
evaporate, and examine the residue. Rub a little between 
the fingers. Burn a little on the end of a glass rod. Note 
each result. 

III. Protein. — (Note. — Use two or more of these tests.) 
(a) Grind the sample with 20 cc. of water in a mortar, pour 

off the water (filter, if not clear). To about 5 cc. of the dilute 
extract add an equal volume of sodium hydroxide solution 

108 



and shake well. Then add drop by drop a very dilute copper 
sulfate solution. A violet color is produced. Note each result. 

(b) To 5 cc. of the extract from (a) add an equal volume of 
concentrated nitric acid. Heat gently until a yellow pre¬ 
cipitate, or a yellow solution, is obtained. Cool in running 
water and add an excess of sodium hydroxide solution. An 
orange color is produced. Note each result. 

(c) To 5 cc. of the extract from (a) add concentrated nitric 
acid slowly, pouring the acid down the inside of the tube 
so the two solutions will not mix. A white cloudy pre¬ 
cipitate is formed at the surface where the two liquids meet. 
Note each result. 

Write the results of these tests in tabular form in your lab¬ 
oratory notes. 


SUPPLEMENTARY EXERCISES ON BROMINE 
AND IODINE 

Supplementary Exercise 44 — Preparation and Properties of 
Bromine — Teacher’s Exercise 

Materials. — Potassium bromide, manganese dioxide, dilute sul¬ 
furic acid. 

Apparatus. — As in Fig. 72; bottle half full of water and fitted 
with a cork. The large test tube has a one-hole rubber stopper to 
which is fitted the bent glass tube; the 
total length of the glass tube is about 
30 cm. (12 in.). 

Caution. — Bromine is a corrosive 
liquid, which readily forms a suffo¬ 
cating vapor. Perform all exercises 
with bromine carefully in the hood. 

Put about 3 gm. of potassium 
bromide in a large test tube, and add 
10 cc. of dilute sulfuric acid. Insert 
the stopper and its tube (Fig. 72), 
attach the test tube holder, and warm 
gently. Bromine vapor soon appears 
in the test tube and, if the heat is sufficient, some vapor 
will escape from the delivery tube. 

109 



Fig. 72. — Apparatus for 
preparing bromine 






Note the color and very cautiously the odor of the bromine 
vapor. Note also if it is heavier or lighter than air. Hold 
a moist piece of bright colored cloth or paper in the vapor, 
and note the effect on the color. 

Continue to heat, and regulate the temperature so that the 
vapor will condense and collect in the bend A of the delivery 
tube. When no further heating produces bromine vapor in 
the test tube, transfer the bromine from the delivery tube 
into a bottle half full of water by holding the end of the 
delivery tube over the mouth of the bottle and heating the 
test tube slightly; the expanding gases will force the liquid 
bromine out of the bend into the bottle. 

Observe the physical properties of the liquid bromine, 
especially the color, solubility in water, heaviness (com¬ 
pared with water), and volatility. As soon as these ob¬ 
servations have been made, cork the bottle tightly and 
shake it vigorously. Observe the solubility of bromine in 
water. 

Note. — In the hood wash the delivery tube free from 
bromine, taking care to get none on the hands. Wash the 
test tube and throw the contents of the test tube into a 
waste jar in the hood. 

Write in your laboratory notes (1) the equation for preparing 
bromine and (2) a summary of the properties of bromine. 


Supplementary Exercise 45 — Preparation and Properties of 
Bromine (Short Method) 

Materials. — Potassium bromide, manganese dioxide, dilute 
sulfuric acid, bright colored paper. 

Caution. — See Supplementary Exercise 44. 

Put a little powdered potassium bromide and twice its bulk 
of manganese dioxide in a test tube, and mix by shaking. 
Add 5 cc. of dilute sulfuric acid, or just enough to moisten the 
mixture well. Attach a test tube holder and heat gently. 
Bromine vapor is evolved. 

Note the color and very cautiously the odor. 

110 


If the vapor condenses on the inside of the test tube, note 
the color and heaviness of the liquid bromine. 

Stand the test tube in the test tube rack, hold a moist 
piece of bright colored paper in the bromine vapor, and note 
the effect on the paper. 

Write in your laboratory notes (1) the equation for the prep¬ 
aration of bromine and (2) a summary of the properties of 
bromine. 


Supplementary Exercise 46 — Tests for Free Bromine and 
for Bromine Combined in a Bromide 

Materials. Potassium bromide (solid and solution), silver 
nitrate solution, carbon tetrachloride, chlorine water (see Ap¬ 
pendix, § 13, List G.), bromine water (for ( a )). 

(a) To 5 cc. of dilute bromine water add 5 cc. of carbon 
tetrachloride, shake well, and note the color of the carbon 
tetrachloride (lower layer), which is caused by free bromine. 

_ Q>) Add a little concentrated sulfuric acid to a little potas¬ 
sium bromide in a test tube; warm slightly, if the action is 
not marked. Observe the result, noting especially the color 
of the liquid or of th$ vapor just above the liquid. 

(c) Add 5 cc. of potassium bromide solution to a test tube 
half full of water, then add a little silver nitrate solution, 
and shake. Observe the properties of the precipitate, espe¬ 
cially the color and texture. 

Test the precipitate by warming a little of it in ammonium 
hydroxide. Note the ease or difficulty of dissolving. Com¬ 
pare silver bromide and silver chloride (Exercise 26 (c)) in 
this respect. 

{d) To 5 cc. of a solution of potassium bromide add a little 
chlorine water and a few drops of carbon tetrachloride, and 
shake. Note the color of the carbon tetrachloride (lower 
layer), which is caused by the liberated bromine. 

Write in your laboratory notes concise statements of the tests 
for (1) free bromine and (2) combined bromine. 

Ill 


4 


Supplementary Exercise 47 — Preparation and Properties of 
Iodine — Teacher’s Exercise 

Materials. — Potassium iodide, manganese dioxide, concentrated 
sulfuric acid, cotton, alcohol, carbon tetrachloride, potassium 
iodide solution. 

Apparatus. — As in Fig. 73. 

Grind together in a mortar about 3 gm. of potassium iodide 
and 5 gm. of manganese dioxide. Put the mixture in a test 
tube, add about 3 cc. of water, 5 cc. of concentrated sulfuric 
acid, and mix well. Clamp the test tube vertically to an 
iron stand (Fig. 73). Close the inner end 
(A in Fig. 73) of the stem of the funnel with 
a small plug of cotton. Hold, or place, the 
funnel over the mouth of the test tube, and 
heat the test tube gently. The vapor of the 
liberated iodine will fill the test tube, and 
crystals will form in the upper part of the 
test tube and in the funnel. Continue to 
heat until enough iodine for several exercises 
collects in the funnel. Scrape the crystals 
into a dish. 

(a) Observe the color of the solid and of 
the vapor, and the odor ( cautiously ). 

( b) Determine the volatility by putting 
a small piece in a test tube and heating 
gently. 

(c) Heat a small piece quickly in a dry test tube, invert the 
test tube when it is full of vapor, and note what the result 
shows about the heaviness of iodine vapor. 

(i d ) Touch a crystal with the finger, and note the color of 
the stain. 

(e) Determine the solubility by shaking a small piece 
separately in 5 cc. of water, alcohol, carbon tetrachloride, 
and potassium iodide solution. Note these results. 

Note. — If crystals are left, use them in the next exercise. 
If not used at once, preserve the iodine in a stoppered bottle. 

Write in your laboratory notes (1) the equation for preparing 
iodine and (2) a summary of the properties of iodine. 

112 


5 


Fig. 73. — Appa¬ 
ratus for prepar¬ 
ing iodine 













Supplementary Exercise 48 — Preparation and Properties of 
Iodine (Short Method) 

Materials. — Potassium iodide, manganese dioxide, concentrated 
sulfuric acid. 

Proceed as in Supplementary Exercise 45 using potassium 
iodide in place of potassium bromide. Note the color and 
cautiously the odor of the vapor. Note the easy condensation 
of iodine vapor and the color of the condensed iodine. Omit 
the bleaching test. 

Write in your laboratory notes (1) the equation for the prepara¬ 
tion of iodine and (2) a summary of the properties of iodine. 

Supplementary Exercise 49 — Tests for Free Iodine 

Materials. — Very dilute iodine solution, carbon tetrachloride, 
cold starch mixture. 

(a) Add a few drops of carbon tetrachloride to 5 cc. of 
very dilute iodine solution. Shake well, and observe the 
color of the carbon tetrachloride (lower layer) which is caused 
by free iodine. 

(b) Add 5 cc. of a cold starch mixture to a test tube nearly 
full of water, and then add a few drops of very dilute iodine 
solution. Note the color. Pour about 5 cc. of the liquid into 
a test tube nearly full of water and shake. Note the color. 
(The blue color is due to the action of free iodine on starch. 
This is a delicate test for both iodine and starch.) 

Write in your laboratory notes the two tests for free iodine. 

Supplementary Exercise 50 — Tests for Iodine 
Combined in an Iodide 

Materials. — Potassium iodide (solid and solution), chlorine water, 
cold starch mixture, carbon tetrachloride, silver nitrate solution. 

(a) Add a little concentrated sulfuric acid to a little 
potassium iodide in a test tube. Observe the result, espe¬ 
cially the color of the vapor. 

113 


(6) Add a few drops of carbon tetrachloride to a very dilute 
solution of potassium iodide. Then add several drops of 
chlorine water, and shake well. Note the color of the carbon 
tetrachloride (lower layer). 

(c) Add 5 cc. of cold starch mixture to 10 cc. of a dilute 
solution of potassium iodide. Add a few drops of chlorine 
water, and shake well. Observe the result, especially the 
color. 

( d) To 5 cc. of potassium iodide solution, add a little silver 
nitrate solution, and shake. Observe the properties of the 
precipitate, especially the color and texture. Test the 
solubility of a little of the precipitate in ammonium hy¬ 
droxide, and note the result. Compare the solubility of 
silver iodide in ammonium hydroxide with silver chloride 
and silver bromide (see Exercise 26 (c) and Supplementary 
Exercise 46 (c)). 

Write in your laboratory notes concise statements of the tests 
for iodine combined in an iodide. 

SUPPLEMENTARY EXERCISES ON SODIUM 

Supplementary Exercise 51 — Preparation and Properties of 
Sodium Bicarbonate — Teacher’s Exercise 

Materials. — Ammonium carbonate, ammonium hydroxide, so¬ 
dium chloride. 

Apparatus. — Carbon dioxide generator (see Fig. 74). 

I. Preparation. — Put 8 gm. of powdered ammonium 
carbonate and 75 cc. of ammonium hydroxide into a bottle; 
add about 35 gm. of fine sodium chloride, cork the bottle, 
and shake the mixture vigorously until most of the solid has 
dissolved. Pour off the clear solution into the bottle C 
(Fig. 74). 

Construct a carbon dioxide generator (see Supplementary 
Exercise 39) like that shown in Fig. 74. Put about 20 gm. of 
marble in the generator bottle A, 25 cc. of water in the 
tube B, introduce dilute hydrochloric acid as usual, and pass 
carbon dioxide slowly through the solution in the bottle C 

114 


from thirty to forty-five minutes (or less, if a precipitate 
forms). Then remove the generator, cork the bottle C, and 
let it stand an hour or more to allow the sodium bicarbon¬ 
ate to settle out of the solution. 

Filter, and wash quickly with a 
very little cold water. Dry the 
precipitate between filter paper. 

(Note. — If only a little of the 
precipitate is formed, use sodium 
bicarbonate from the laboratory 
bottle for II.) 

II. Properties. — (a) Apply to 
small portions of the precipitate 

(1) the flame test for sodium and Fig - 74 - — Apparatus for pre- 

(2) the usual test for a carbonate. f r a 0 ™| cid carbon dioxide free 
State the results. 

(6) Put a little on moist litmus paper (both colors). Note 
the result. 

(c) Heat a little in a test tube inclined so that the open 
end is the lower. Note the visible product. Apply the usual 
test for carbon dioxide to the gas in the test tube; note the 
result. Continue to heat until there is no further evidence of 
change. Determine what the final residue is by applying to 
it tests for sodium, a bicarbonate as in (a) and (6), and sodium 
carbonate ( e.g . litmus test). Note the results. 

Write a brief account of I in your laboratory notes. 

Write also a summary of the properties of sodium bicarbonate 
based on II. 

Supplementary Exercise 52 — Preparation of Sodium 
Chloride in Four Ways — Teacher’s Exercise 

Materials. — Sodium, sodium carbonate, sodium sulfate solution, 
barium chloride solution. 

Apparatus. — Chlorine generator, deflagrating spoon. 

A. Direct combination. Prepare a bottle of chlorine in 
the hood. Remove a lump of sodium from the bottle, cut 
off a small piece, put the lump back, cover the small piece 

115 





















with a mortar. Put a little sand or a bit of asbestos in the 
bowl of a deflagrating spoon, lay the sodium on it, heat gently 
until it melts and begins to burn, then lower the spoon care¬ 
fully into the bottle of chlorine. Vigorous chemical action 
takes place. As soon as it is over, remove the spoon and put 
it in a safe place. Note the white product in the bottle. 
Scrape out some, taste it, and decide what it is. 

B. Neutralization. As in Exercise 29. 

C. By Forming a Volatile Product. Put a small lump of 
sodium carbonate in an evaporating dish, carefully add dilute 
hydrochloric acid, and stir until effervescence (bubbling of 
gas) ceases. Evaporate to dryness, redissolve the product 
in a little water, evaporate again, and find out what the 
product is by (1) tasting cautiously and (2) testing flame 
test and precipitation test (for a chloride). Note the 
results. 

D. By Forming an Insoluble Product. To 15 cc. of sodium 
sulfate solution add barium chloride solution slowly, and 
stop between additions to let the precipitate settle. Con¬ 
tinue to add the barium chloride solution until precipitation 
ceases. Let the precipitate settle. Pour off the clear liquid, 
and test it for sodium chloride, i.e., by flame test and precipi¬ 
tation test. Note the results. 

W rite in your laboratory notes a summary of the four ways of 
preparing sodium chloride. 

Write also the equation for each reaction. 


CALCIUM COMPOUNDS 

^Exercise 57 — Properties of Calcium Carbonate, Calcium 
Oxide, and Calcium Hydroxide 

Materials. — Calcium carbonate, calcium oxide; sodium carbonate 
and calcium hydroxide solutions. 

A. Calcium Carbonate, (a) Put a drop or two of dilute 
hydrochloric acid on one or more specimens of calcium car¬ 
bonate. Note the result in each case. Conclude what gas 

116 


is evolved. (This reaction is the usual test for a car¬ 
bonate.) 

(6) Attach a small lump of marble to a test wire, or 
lay it on a wire gauze, and heat it intensely for ten or 
fifteen minutes. Test it for a carbonate and note the 
result. 

(c) Add 5 cc. of sodium carbonate solution to 5 cc. of cal¬ 
cium chloride solution. Note the precipitate. Decide what 
it is. (This reaction is often used as a test for soluble car¬ 
bonates.) 

B. Calcium Oxide and Hydroxide. I. Preparation. — 

(a) Prepare calcium oxide as in A (b ). Let the residue cool, 
put it in an evaporating dish, and add a little water. Observe 
the result. Test the liquid with red litmus paper. Apply 
the flame test for calcium. Note the results. 

(b) Prepare solid calcium hydroxide by adding a small 
amount of water slowly to a lump of lime. Save for III. 

II. Properties of Calcium Oxide. — (a) Put a large lump 
of fresh calcium oxide on a glass plate or block of wood and 
let it remain exposed to the air for a few days. Examine it at 
intervals and note the change. Conclude as to the effect 
of air on calcium oxide. 

( b) Pour water upon a lump of fresh calcium oxide and 
note any change in temperature. Decide upon an explana¬ 
tion of the change, if any. 

III. Properties of Calcium Hydroxide. — (a) Add a little 
solid calcium hydroxide to a test tube half full of water and 
shake vigorously. Let the suspended solid settle somewhat, 
and filter. Pour half the filtrate into an evaporating dish 
and evaporate it to dryness; save the other half. (Mean¬ 
while perform ( b ).) When evaporated, compare the amount 
of residue in the dish with the amount of solid originally 
shaken with water. Draw a conclusion regarding the solu¬ 
bility of calcium hydroxide in water. 

(6) Taste cautiously of the solution saved from (a), and 
describe the taste. Determine the reaction toward litmus. 
Heat the solution slowly to boiling, and note the result. 
Conclude as to the effect of increased heat on the solubility 
of calcium hydroxide in water. 

117 ‘ 


(c) (1) Expose calcium hydroxide solution to the air, and 
(2) exhale the breath through calcium hydroxide solution 
(Fig. 75). Note each result. Conclude 
what is the product. 

Write a brief explanation of the results 
in A (a), ( b ), (c) in your laboratory notes , 
including the verbal and chemical equa¬ 
tions. 

Write answers to these questions in your 
laboratory notes. (1) What calcium com¬ 
pound is formed by heating calcium car¬ 
bonate? What is the equation? (2) What 

substance in air produces the marked change 
in calcium oxide ? (3) In calcium hydroxide 

solution? (4) What are the equations for 
I (b), II (a), III (c)? (5) What is the reac¬ 

tion of calcium hydroxide toward litmus? 
(6) What is the effect of increased heat on the solubility of 
calcium hydroxide? 



Fig. 75. ■— Breath¬ 
ing into calcium 
hydroxide solu¬ 
tion 


^Exercise 58 — Calcium Compounds and Hardness of Water 
— Teacher’s Exercise 

Materials. — Calcium hydroxide, solutions of soap, calcium 
sulfate, sodium carbonate, and borax. 

Apparatus. — Carbon dioxide generator (see Fig. 69, Supplemen¬ 
tary Exercise 39). 

A. Temporary Hardness. — Prepare a solution of acid 
calcium carbonate by passing carbon dioxide free from hydro¬ 
chloric acid into a mixture of 25 cc. of saturated calcium 
hydroxide and 25 cc. of water until the precipitate formed is 
redissolved. 

(a) To 15 cc. of the clear acid calcium carbonate solution 
add 5 cc. of soap solution. Shake well and observe the 
product. Rub some between the fingers and note the result. 

iff) Boil vigorously 15 cc. of acid calcium carbonate solu¬ 
tion for a few minutes, filter, and add 5 cc. of soap solution. 
Shake well and observe the result. Compare the results of 
(a) and (6). 


118 







(c) To 10 cc. of clear acid calcium carbonate solution add 
5 cc. of saturated calcium hydroxide, shake, filter, and to the 
clear filtrate add 5 cc. of soap solution. Shake well and 
observe the result. Compare the results of (a), ( b ), and (c). 

B. Permanent Hardness. — (a) Proceed as in A (a), 
using 15 cc. of calcium sulfate solution (instead of acid calcium 
carbonate solution). Compare the results of B (a) and A (a). 

( b) Boil 15 cc. of calcium sulfate solution, add 5 cc. of soap 
solution, and shake. Compare the results of B (cl), (b), and 
A (6). 

(c) To 15 cc. of calcium sulfate solution add 10 cc. of 
sodium carbonate solution, filter, add 5 cc. of soap solution, 
and shake well. Compare the results of B (6) and B (c). 

C. Try the effect of (a) ammonium hydroxide (in excess, 
as told by the odor), and (6) borax solution on both tem¬ 
porarily and permanently hard water. Note the result. 

Write a brief account of this exercise in your laboratory notes, 
(1) designating the parts by letters and (2) making a brief general 
statement about each kind of hard water. 

SUPPLEMENTARY EXERCISES ON 
CALCIUM COMPOUNDS 

Supplementary Exercise 53 — Tests for Calcium in 
Compounds 

Materials. — Calcium compounds (powdered), ammonium oxalate 

and sodium carbonate solutions. 

(a) Apply the flame test to several calcium compounds, 
using a clean test wire in each case. Observe the color of the 
flame and decide upon an accurate name for it. (Note. — 
The chloride gives a typical result.) 

( b ) Add an excess of ammonium oxalate solution to calcium 
chloride solution, and note the result. The precipitate is 
calcium oxalate. Divide it into two parts. To (1) add an 
excess of dilute hydrochloric acid, warm gently, and note the 
final result. To (2) add considerable acetic acid and warm 
gently; note the final result and compare with (1), 

119 


(c) Add an excess of sodium carbonate solution to calcium 
chloride solution, and note the result. Decide what the 
precipitate is. Divide it into two parts, and treat with the 
acids as in (6). Note the results and compare with ( b ). 

(, d ) Suggest a way to test for calcium in calcium carbonate 
and calcium sulfate. Try it, and record the result in your 
laboratory notes. 

( e ) Optional. Apply tests for calcium to one or more of 
these: Mortar, plaster, tooth powder, cement, whiting. 
Record each result. 

Write a brief statement of the distinctive tests for calcium in 
your laboratory notes. 


Supplementary Exercise 54 — Properties of Cement — 
Teacher’s Exercise 

Materials. — Cement, sand, 2 elastic bands. 

(a) Mix a little cement with enough water to form a thick 
paste, and spread a thin layer on a block of wood or a glass 
plate. Let it remain undisturbed for a day or more. Then 
examine, and note the condition of the cement. 

(i b ) Prepare two paper cylinders (about 8 cm. (or 3 in.) 
long) by rolling a piece of paper around a test tube. Close 
one end of each by folding over the 
edges of the paper. 

Fill an evaporating dish not quite 
half full of cement, add about the same 
bulk of sand, and mix well. Add water 
and stir until a soft paste is formed. 
Pour the mixture into each paper cylin¬ 
der until full and slip an elastic band 
over the upper end to hold the paper in place. Lower one 
cylinder into a bottle of water and the other into an empty 
bottle (Fig. 76). Let both stand for a day or two. Then 
remove, unroll the paper, and compare the contents. 


F\ f=\ 



Fig. 76. — Testing 
cement 


Write a brief account of this exercise in your laboratory notes. 
120 









Supplementary Exercise 55 — Plaster of Paris — 
Teacher’s Exercise 

Materials. — Plaster of Paris, vaseline. 

Mix a little plaster of Paris with enough water to form a 
thick paste. Put the paste on a block of wood or a glass 
plate. Rub a very little vaseline on one side of a coin, and 
press the coin, coated side down, into the paste. Let it re¬ 
main undisturbed for fifteen or more minutes. Then remove 
the coin carefully, and examine the hardened plaster. 

Write a brief account of this exercise in your laboratory notes. 
IRON 

Exercise 59 — Tests for Iron Salts 

Materials. — Solutions of ferrous sulfate (prepared as needed from 

crystals which have been thoroughly washed in cold water), am¬ 
monium hydroxide, potassium ferricyanide, ferric chloride, 

potassium ferrocyanide, and potassium thiocyanate. 

A. Ferrous Salts. — (1) Add 5 cc. of ammonium hy¬ 
droxide to 5 cc. of ferrous sulfate solution. Shake well. 
The precipitate is ferrous hydroxide. Note the color at 
once. Shake, and note the changes in color. 

(2) Add 5 cc. of potassium /emcyanide solution to 5 cc. 
of ferrous sulfate solution. Shake well. The precipitate is 
ferrous ferricyanide. Note the color. (This is the best test 
for a ferrous salt.) 

B. Ferric Salts. — (1) Add 5 cc. of ammonium hydroxide 
to 5 cc. of ferric chloride solution. The precipitate is ferric 
hydroxide. Note the color and texture. 

(2) Add 5 cc. of potassium ferrocyanide solution to 5 cc. 
of ferric chloride solution. The precipitate is ferric ferro¬ 
cyanide. Note the color and texture. 

(3) Add 5 cc. of potassium thiocyanate solution to 5 cc. 
of ferric chloride solution. Note the result. The red colored 
solution is due to soluble ferric thiocyanate. (This is the 
best test for a ferric salt.) 


121 


C. Try (a) potassium ferricyanide and ferric chloride and 
(6) potassium thiocyanate and ferrous sulfate. 


Write the results of this exercise in your laboratory notes in 
tabular form, thus : — 


Iron 

Ammonium 

Potassium 

Potassium 

Potassium 

Salt 

Hydroxide 

Ferricyanide 

Ferrocyanide 

Thiocyanate 

A. Ferrous 

B. Ferric 






Write also in your laboratory notes the best test for (1) ferrous 
and (2) ferric salts. 


Exercise 60 — Reduction and Oxidation of Iron Salts 

Materials. Ferric chloride solution, ferrous sulfate solution 
(freshly prepared from crystals washed with cold water), potas¬ 
sium chlorate, zinc. 

A. Reduction. — Put a piece of zinc in 10 cc. of ferric 
chloride solution, and add a few drops of concentrated 
hydrochloric acid. Warm gently about ten minutes, and 
test separate portions of the solution for a ferrous and a 
ferric salt (use the best single test). Note the results. 

B. Oxidation. — (a) To 10 cc. of the freshly prepared 
ferrous sulfate solution add a few drops of concentrated 
hydrochloric acid, three or four crystals of potassium chlo¬ 
rate, and warm gently about five minutes. Test separate 
portions of the solution for a ferrous and a ferric salt. Note 
the results. 

(6) Add a few drops of concentrated sulfuric acid to 10 cc. 
of ferrous sulfate solution, shake and then add 10 cc. of con¬ 
centrated nitric acid drop by drop. Boil carefully. Test 
as in (a) and note the results. 

Write a brief account of this exercise in your laboratory notes. 

122 












METALS — DISPLACEMENT AND TESTS 

^Exercise 61 — Displacement of Metals 

Materials. — Copper wire and strips of zinc, solutions of copper 

sulfate, mercuric chloride (Poison), silver nitrate, lead nitrate. 

(a) Put a clean copper wire in a test tube half full of 
mercuric chloride solution (Poison). After a short time 
remove the wire and observe the deposit. 

(b) Proceed as in (a) with copper wire and a solution of 
lead nitrate. Note the deposit, if any. 

( c ) Proceed as in (a) using a strip of zinc and the solutions 
separately. Note the results. 

Write a very brief account of this exercise in your laboratory 
notes. 

Write also a list of the metals in the order of their displace¬ 
ment by ( 1) copper and (2) zinc. 

Exercise 62 — Flame Tests for Metals 

Materials. Sodium, potassium, calcium, and barium chlorides, 

strontium nitrate, metallic copper and zinc. 

Apparatus. — Test wire. 

(a) Review. Recall or review the results of heating salts 

of the metals sodium, potassium, calcium, and barium on a 
clean test wire. If in doubt, predict the color and verify by 
tests. v 

(b) Heat a bit of strontium nitrate on a clean test wire in 
the flame, and note the color. Compare with the color due 
to calcium and note (1) the resemblance and (2) the dif¬ 
ference. Decide upon a name for the strontium color. 

(c) Heat a copper wire in the hot part of the Bunsen flame 
and note the color. Decide upon a name for it. 

(d) As in (c), using a strip of zinc and taking care £o tilt the 
burner so that melted zinc will not drop inside. Note the 
color. Compare with the color from copper. Decide upon 
a name for the color. 

( e ) Test unknowns and note the results. 

123 


Write the results of this exercise in your laboratory notes in 
this form : — 


Compound or Metal 

Color op Flame 

Compound or Metal 

Color op Flame 

1 . 


6. 


2. 


7. 


3. 


8. 


4. 


9. 


5. 


10. 



SUPPLEMENTARY EXERCISES ON METALS 

Supplementary Exercise 56 — Tests for Metals 

Materials. — For A aluminum sulfate or alum solution. For B 
copper sulfate and potassium ferrocyanide solutions, acetic acid. 
For C magnesium sulfate, ammonium chloride, and disodium 
phosphate solutions. For E mercuric chloride, mercurous nitrate, 
stannous chloride solutions. For G lead nitrate, hydrogen 
sulfide and potassium dichromate solutions. For J manganese 
sulfate and ammonium sulfide solutions. For K gold chloride 
and stannous chloride solutions. 

Test “ unknowns ” for these metals. 

A. Aluminum. — Add ammonium hydroxide to a solution 
of an aluminum salt ( e.g . aluminum sulfate or alum), and 
shake well. The precipitate is aluminum hydroxide. Note 
its color and texture. 

B. Copper. — (1) Add considerable ammonium hydrox¬ 
ide to a solution of a copper salt (e.g. copper sulfate), and 
shake well. Note the final solution, especially the color. 

(2) To 5 cc. of dilute copper sulfate solution add a few 
drops of acetic acid and of potassium ferrocyanide solution. 
Note the precipitate (cupric ferrocyanide, Cu 2 Fe(CN) 6 ), 
especially the color. 

C. Magnesium. — To 5 cc. of a solution of a magnesium 
salt (e.g. magnesium sulfate) add in succession ammonium 
chloride, ammonium hydroxide, and disodium phosphate 
solutions. Note the precipitate (ammonium magnesium 
phosphate, NH 4 MgP0 4 ), especially the color and texture. 

124 














D. Zinc. — See Supplementary Exercise 9. 

E. Mercury. — (1) Mercuric compounds, (a) To 5 cc. 
of dilute mercuric chloride solution (Poison) add a little 
ammonium hydroxide, shake well, and note the color of the 
precipitate. 

(b) To 5 cc. of dilute mercuric chloride solution (Poison) 
add a little stannous chloride solution and note the precipi¬ 
tate ; then add considerable stannous chloride solution and 
note the final result. The black precipitate is finely divided 
mercury. 

(2) Mercurous compounds, (a) Proceed as in (1) (a), 
using mercurous nitrate solution, and note the difference, 
especially the color. 

(6) Add dilute hydrochloric acid to mercurous chloride 
solution and note the color of the precipitate. Then add 
considerable ammonium hydroxide (to alkaline reaction — 
test with red litmus paper), shake well, and note the color 
of the final product. 

F. Tin. —See E (1) (6). 

G. Lead. — (1) Add a little hydrogen sulfide water to a 
solution of a lead salt ( e.g. lead nitrate). Note the precipitate 
(lead sulfide, PbS), especially the color. 

(2) As in (1), using dilute sulfuric acid. 

(3) As in (1), using potassium dichromate solution. 

H. Silver. — See Exercise 26. 

I. Chromium. — See G (3). 

J. Manganese. — (1) Add a little ammonium sulfide 
solution to a manganese salt (e.g. manganese sulfate) solution 
and note the precipitate (manganese sulfide, MnS), especially 
the color. 

K. Gold. — Obtain a solution of gold chloride (or pre¬ 
pare it as in Supplementary Exercise 23) . Heat the solution 
in the hood to drive off free chlorine and the nitric acid, 
dilute with water, and add slowly a little dilute stannous 
chloride solution. Note the purple (or black) precipitate of 
finely divided gold. If very dark, add considerable water 
and shake well. 


Write a brief statement of each test in your laboratory notes. 
125 


Supplementary Exercise 57 — Tests with Borax Beads 

Materials. — Powdered borax, cobalt nitrate, copper sulfate, and 
manganese sulfate solutions. 

Apparatus. — Test wire, lens. 

Heat the looped end of a clean test wire (preferably plati¬ 
num— see Appendix, §5 (d)), and dip it into powdered borax. 
Heat the adhering borax in the flame, rotating the wire slowly, 
until no further change is apparent; continue to dip it into 
the borax and heat in the flame until a small bead is formed. 

(a) Cobalt Compounds. — Moisten a borax bead with 
cobalt nitrate solution. Heat the bead in the oxidizing part 
of the Bunsen flame (Fig. 77 left); rotate the bead while 




Fig. 77. — Testing with borax beads — oxidizing left, and reducing right 

heating it. Note the color of the cold bead. If it is black, 
melt in a little more borax; if faintly colored, moisten again 
with the cobalt nitrate solution. The color is readily 
detected by looking at the bead against a white object in a 
strong light, or by examining it with a lens. 

When the color has been definitely determined, heat the 
bead in the reducing flame (Fig. 77 right). Compare the 
color of the cold bead with the previous observation. Note 
the result. 

Remove the bead from the wire by dipping it, while hot, 
into water and then rubbing or scraping it from the wire. 

(6) Copper Compounds. — Make another bead and pro¬ 
ceed as in (a), using copper sulfate solution. Compare the 
colors of the cold beads. 

(c) Manganese Compounds. — Proceed as in (a) with 
another bead and manganese sulfate solution. Compare 
the colors of the cold beads. 

126 












Write the results of this exercise in your laboratory notes 
in tabular form, thus : — 


Name op Compound 

Color op Cold Bead 

Oxidizing Flame 

Reducing Flame 

(a) 



( b ) 



(c) 



(d) 




Supplementary Exercise 58 — Cobalt Nitrate Tests 

Materials. — Aluminum sulfate, magnesium sulfate, zinc sulfate, 
cobalt nitrate solution, charcoal block. 

Apparatus. — Blowpipe, blowpipe tube. 

(а) Aluminum. — Heat a little aluminum sulfate (or any 
other aluminum compound) on charcoal in the blowpipe 
flame (oxidizing part — A in Fig. 4 68). Cool, and moisten 
with a drop or two of cobaltous nitrate solution. Heat 
again, and note the color of the residue on the charcoal. 

(б) Zinc. —Proceed as in (a), using zinc sulfate (or any 
other zinc compound). Note the color of the residue. 

(c) Magnesium. — Proceed as in (a), using magnesium 
sulfate. Note the color of the residue. 

Write in your laboratory notes a brief statement of the 
cobalt nitrate tests for (a) aluminum, (b) zinc, and (c) mag¬ 
nesium. 

Supplementary Exercise 59 — Testing Salts for the Metal 
and Non-Metal 

Materials. — Chlorides, sulfates, carbonates, and nitrates of 
sodium, potassium, calcium, barium, and ammonium; bromide 
and iodide of potassium; nitrates of silver, lead, and mercury 
(ous); dilute hydrochloric acid. 

Obtain several unknowns from the substances enumerated 
above and test separate portions of each for (a) the metal 

127 

















part, i.e. sodium, potassium, calcium, barium, silver, lead, 
ammonium, and ( b ) the non-metal part, i.e. chloride, sulfate, 
nitrate, bromide, iodide, and carbonate. Note each result. 


Write the results of this exercise in your laboratory notes in 
this tabular form : — 


Number of Substance 

Metal Part 

Non-metal 

Part 

Name of 
Substance 

Formula 

1 . 

2. 

Etc. 






Supplementary Exercise 60 — Silver Salts and Photography 
— Teacher’s Exercise 

Materials. — Solutions of silver nitrate (17 gm. to a liter), sodium 
chloride (5.8 gm. to a liter), and sodium thiosulfate — “hypo” 
(250 gm. to a liter) ; commercial developer or a substitute (see 
Appendix, § 13, List G) * 

Apparatus. — 4 test tubes (labeled), black paper; for (/), 2 plates 
(preferably lantern slide plates), and photographic paper. 

Note. — Owing to the rapid action of silver bromide, 
silver chloride is used in (a) to (d). 

(a) Add 5 cc. of the silver nitrate solution to 5 cc. of the 
sodium chloride solution, shake gently, and note the time 
(by a watch). Expose the precipitate to the light. Examine 
frequently and note the time needed for a definite change in 
color. 

( b ) Precipitate silver chloride as in ( a ) and add also 5 cc. 
of the developer. Note the time. Expose and note the 
final time as in (a). Compare the times needed for the 
change. 

(c) Wrap a piece of dark paper around a test tube to pro¬ 
tect it from the light, and add the three solutions as in (5). 
After half a minute, examine quickly and note the color. 
Examine again after half a minute more. Compare with (5). 

(d) Precipitate silver chloride as in (a), add also 5 cc. of 
“ hypo ” solution, and shake well. Note the result. 

128 













(e) Optional. Try (a) to (d) with silver bromide (pre¬ 
pared from dilute silver nitrate and potassium bromide solu¬ 
tions) and compare the results with (a) to (d). 

(/) Expose two photographic plates (preferably lantern 
slide plates) or films, develop both in the dark room with the 
class, fix one, and later compare both. Make two prints 
from the fixed plate, and develop. Wash one, and later 
compare the two prints. 

Write an account of this exercise ((a) to {d)) in your labora¬ 
tory notes. 

Write also the results of (e) and (/), if done. 

Supplementary Exercise 61 — Preparation and Properties of 
Aluminum Hydroxide 

Materials. — Solutions of aluminum sulfate, sodium hydroxide, 

cochineal, and aluminum acetate; turbid water, alizarin paste, 

cotton cloth. 

(а) Add 5 cc. of ammonium hydroxide to 5 cc. of aluminum 
sulfate solution, shake, and note the precipitate of aluminum 
hydroxide. 

(б) To 5 cc. of aluminum sulfate solution (1) add a very 
little sodium hydroxide, shake, and note the result, and then 
(2) add considerable sodium hydroxide, shake, and note the 
result. 

(c) Fill a test tube half full of turbid water (prepared by 
shaking fine clay with water), add 5 cc. of aluminum sulfate 
solution, shake well, add 10 cc. of ammonium hydroxide 
solution, and mix well by stirring. Let the mixture stand 
about ten minutes, and then compare the upper part of the 
liquid with the sample of turbid water. Note the difference. 

(i d ) Add a little aluminum sulfate solution to a dilute 
solution of cochineal, then add ammonium hydroxide, and 
shake well. Filter, and compare the colors of the filtrate 
and precipitate. 

( e ) Boil two small pieces of cotton cloth for several 
minutes thoroughly in water. Remove the excess of water. 
(1) Put one piece in a dish or beaker, add 50 cc. of water and 

129 


5 cc. of alizarin paste, and heat nearly to the boiling point 
for about two minutes. Wash the cloth in water, dry, and 
then examine. (2) Proceed in the same way with the other 
piece of cotton cloth which has been previously mordanted 
by boiling for about two minutes in aluminum acetate solu¬ 
tion. Compare the two pieces of cloth as to color. 

Write answers to these questions in your laboratory notes. 

(1) What is a conspicuous property of aluminum hydroxide? 

(2) What are the equations for (a) and ( b ) ? (3) What is a 

test for aluminum hydroxide ? (4) Of what value is aluminum 

hydroxide (a) as a water purifier and ( b) in dyeing ? 


Supplementary Exercise 62 — Qualitative Analysis of a 
Solution of Lead, Silver, and Mercury (ous) 

Materials. — Solution containing lead nitrate, silver nitrate, and 
mercurous nitrate; hydrogen sulfide water, potassium chromate 
solution. 

(a) Precipitation. To 10 cc. of the solution containing the 
three metals (as the ions Pb ++ , Ag + , Hg + ) add dilute hydro¬ 
chloric acid drop by drop until precipitation ceases. 

( b ) Separation of Lead. Allow the mixture of precipitated 
chlorides to settle, pour off the liquid carefully, add about 15 
cc. of water, boil, and filter. This operation dissolves most 
of the lead chloride. Test the filtrate for lead as in (c) ; 
save the precipitate for ( d ). 

(c) Test for Lead. To separate portions of the filtrate add 
hydrogen sulfide water and potassium chromate solution 
The two solid products are lead sulfide and lead chromate. 
Note the color of each precipitate. 

(i d ) Separation of Silver and Mercury. Wash the pre¬ 
cipitate from ( b ) with hot water until the wash water does not 
give a test for lead. Then stand the funnel in a clean test 
tube and pour ammonium hydroxide on the mixture of silver 
and mercurous chlorides. This operation dissolves the 
silver chloride. Test the filtrate as in (e); save the pre¬ 
cipitate for (/). 


130 


(e) Test for Silver. To the filtrate from (d) add dilute 
nitric acid to acid reaction and shake. The dissolved silver 
compound is decomposed and the silver is precipitated as 
silver chloride. 

(/) Test for Mercury. The black residue on the paper in 
( d ) is a sufficient test for mercury. Confirm thus: Pour a 
little aqua regia (mixture of 3 cc. of concentrated hydrochloric 
acid and 1 cc. of concentrated nitric acid) upon the black 
precipitate ; catch the filtrate in a porcelain dish, dilute with 
about 5 cc. of water, and add a clean copper wire; remove 
the wire in a few minutes, and mercury will be seen on the wire 
as a bright silvery coating. 

Write in your laboratory notes a very brief outline of the steps 
in this exercise. 

Write also the three equations for (a) and the two for (c). 

Write also from this exercise the test for Pb ++ , Ag + , and 

Hg ++ . 


131 










APPENDIX 


1. The pressure of water vapor in millimeters of mercury 

is : -— 


Tempera¬ 

ture 

Vapor 

Pressure 

Tempera¬ 

ture 

Vapor 

Pressure 

Tempera¬ 

ture 

Vapor 

Pressure 

12 

10.5 

17 

14.4 

22 

19.7 

12.5 

10.8 

17.5 

14.9 

22.5 

20.3 

13 

11.2 

18 

15.4 

23 

20.9 

13.5 

11.6 

18.5 

15.9 

23.5 

21.5 

14 

11.9 

19 

16.4 

24 

22.2 

14.5 

12.3 

19.5 

16.9 

24.5 

22.8 

15 

12.7 

20 

17.4 

25 

23.6 

15.5 

13.1 

20.5 

18.0 

25.5 

24.3 

16 

13.6 

21 

18.5 

26 

25.0 

16.5 

14.0 

21.5 

19.1 

26.5 

25.7 


The numbers in the Vapor Pressure columns are the values 
for a in the formula for the reduction of gas volumes: — 

V'(P' - a) 

760(1 + (0.00366 X t)) 

2. How to use the Bunsen burner. — The Bunsen burner 
(Fig. I) is used as a source of heat, 
tube (A), which should be con¬ 
nected with the gas supply. To 
light the burner, turn on the gas 
and hold a lighted match a short 
distance above the top of the 
burner tube ( B ). The flame 
usually used should have a faint 
blue color. If it is yellow, turn 
the ring at the bottom of the 
burner until the flame is blue. 

A flame of suitable height for most experiments is about 10 
centimeters (or 4 inches). Adjust the gas pressure until the 

133 


It is attached to a rubber 



Fig. I. — Bunsen burner 























flame is about this height. The hottest part of the flame is 
near the top. 

In heating with the Bunsen burner follow these direc¬ 
tions:— . 

(a) Light the burner before a piece of apparatus is held 
over it or before it is placed beneath a wire gauze which 

supports a dish or a flask. 

(b) Test tubes — used fre¬ 



quently — should be dry on the 
outside. As a rule the test 
tube should be attached to a 
test tube holder and held at an 
angle, as in Fig. II. If the 
test tube contains a solid, heat 
gradually by moving the tube 


Fig. II. — Using a test tube in and out of the flame. If the 
holder test tube contains a liquid, only 

the part containing the liquid should be put in (or above) the 
flame. When the liquid begins to boil, the test tube should 
be removed from the flame for an instant or held over it. 

(c) Do not heat empty glass apparatus, e.g. beakers. In 
heating a beaker containing a liquid, do not use the free 
flame, but place the vessel on a wire gauze which stands on an 
iron ring. Porcelain dishes should also be placed on a gauze. 
Porcelain crucibles may be heated with a free flame as 
directed. All glass and porcelain apparatus should be 
heated and cooled gradually. 

3. Cutting, bending, drawing, and closing glass tubing. — 
(a) Cutting. — Determine the length needed, lay the tube 
on the desk, and with forward 



strokes of a triangular file make 
a short, deep scratch where the 
tube is to be cut. Grasp the 
tube in both hands, and hold 


the thumbs together opposite Fig m . _ Cutting a glass tube 
the scratch; now push gently 

with the thumbs, pull at the same time with the hands, 
and the tube will break at the desired point (Fig. III). 
The sharp ends should be smoothed by rotating them 


134 







slowly in the Bunsen flame until a yellow color is distinctly 
seen or until the end becomes red hot; this operation is 

called fire polishing (Fig. IV). 

(b) Bending. — Glass tubes 
can be bent in an ordinary 




Fig. IV. — Fire polishing a glass 
tube 



Fig. V. — A wing top 

illuminating gas flame, but 
if the Bunsen flame is used, 
it should be flattened by a 
wing-top attachment (Fig.V). 
Slip the wing-top upon the top of the burner tube before 
lighting the gas. 

The flattened Bun¬ 
sen flame should be 
slightly yellow and 
about 7 centimeters 
(2.5 inches) wide for 
ordinary bends. 

A right-angle 

bend is easily made. Fig. VI. — Bending a tube into a right angle — 

Determine the part first step 

where the tube is to be bent. Grasp the tube in both hands, 

and hold it so that this part 
is directly over the middle of 
the flame (Fig. VI). Slowly 
rotate it between the thumbs 
and forefingers, and gradually 
lower it into the flame. Con¬ 
tinue to rotate it until the 
glass feels soft and ready to 
bend. Then remove it from 
the flame, and slowly bend 
it into a right angle (Fig. 
VII). Use a square block of 
wood to assist the eye in 



Fig. VII. — Bending a tube into a 
right angle — second step 


135 



















making an exact right angle. The bent part of the tube 
can be annealed (to prevent cracking) by rotating it in a 

yellow flame until it becomes 
coated with soot, and then 
allowing it to cool slowly. 

A tube can be bent into 
a small oblique angle by 
heating it through about 
twice the space required for 
a right angle (Figs. VIII, 
IX). A large oblique angle 
( i.e . a very slight bend) can 
be made by holding the tube 
across the flame, heating 
a short space, and then 
bending slightly. 

(c) Drawing. — Glass 
tubes can be drawn into two 
pointed tubes thus: Heat 
the tube as in ( b ) through 
about 2.5 centimeters 
(1 inch) of its length, re¬ 
move it from the flame and slowly pull it apart a short dis¬ 
tance ; let it cool for a second or two, and then pull it quickly 
to the desired length. 

By using a glass rod, stirring rods can be made in the same 
way, but the rod must be heated for a longer time than the 
tube. 

{d) Closing. — Glass tubes can be closed by holding the 
end in the flame and slowly rotating the tube until the 
glass melts and closes the end. If both ends are to be closed 
(as in making the glass plug for Exercise 27), close one end, 
then draw out the other end, melt off the shorter piece, and 
thicken the remaining end by heating and rotating in the 
flame. 

4. Filtering. — A liquid may be separated from a solid by 
filtering. A circular piece of filter paper (Fig. X -— A) is folded 
to fit a glass funnel, and when the mixture is poured upon 
this paper the solid — called the residue or precipitate — 

133 



Fig. VIII. — Bending a tube into an 
oblique angle — first step 



Fig. IX. — Bending a tube into an 
oblique angle — second step 



















Fig. X. — Folding a filter paper 


is retained, while the liquid — called the filtrate passes 
through and may be caught in a test tube or any other vessel. 

Sometimes the clear liquid is first poured carefully off from 
the precipitate (or other solid) without disturbing the solid 
(see Fig. XIV). This 
operation is called de¬ 
canting, and sometimes 
precedes a final filter¬ 
ing. 

The filter paper is 
prepared for the funnel 
by folding the circular 
piece A (Fig. X) into 
the shapes B and C. 

The folded paper is 
then opened into the 
cone D so that three thicknesses are on one side and one on 
the other. To filter, the cone-shaped paper (D) is placed 
in the funnel E and moistened with water, so it will stick 
to the funnel. The liquid to be filtered may be poured 
directly from the vessel upon the paper or down a glass rod 

(Fig. XIV) which 
touches the edge of 
\I/ the vessel (§6 (a) 

/ w \ below); the lower 

1 "' end of the rod 

should nearly touch 
the paper inside the 
funnel. The funnel 
can be supported 

as shown in Fig. 
XI. 



Fig. XI. — Funnel supported for filtering 


5. Constructing and arranging apparatus. The various 
parts of the apparatus should be assembled and put together 
as completely as possible before starting the exercise. The 
parts that are to fit each other should be connected so 
that all joints are gas-tight. In long exercises or those 
involving weighing, the apparatus should be inspected by the 
Teacher. 


137 





















The following directions should be studied carefully: 

(а) To insert a glass tube into a rubber tube. — Cut one 
end of the rubber tube at an angle, moisten the smoothed end 
of the glass tube with water, place the end of the glass tube 
in the angular-shaped cavity so that both tubes are at about 
a right angle, grasp the upper end of the rubber tube firmly 
and slip it slowly down and over the end of the glass tube. 

(б) To push a glass tube through a hole in the stopper. — 
Dip the stopper in water or wet one end of the tube and grasp it 
firmly near this end ; hold the stopper between the thumb and 
forefinger of the other hand, and carefully work the tube 
through the hole by a gradual rotary motion. Never point 
the tube toward the palm of the hand that holds the stopper. 
Never grasp a bent tube at the bend when inserting it into a 
stopper — it may break and cut the hand severely. 

(c) To bore a hole in a cork. — Select a cork free from 
cracks or channels and use a borer which is one size smaller 
^ than the desired hole. Moisten the 

0 y ' borer with water or soap solution. 

Hold the cork between the thumb and 
forefinger, press the larger end against 
a firm board, and slowly push the borer 
by a rotary movement through the 
cork, taking care to bore perpendicu¬ 
larly to the cork (Fig. XII). If the hole 
is too small, enlarge it with a round 
Fig. XII. — Cork borer gi e . Push the small cylinder of cork 
finally out of the borer with the handle. 

(i d ) To make a test wire. — (1) Platinum. Cut the glass 
rod and wire to the desired length — about 10 centimeters 
(4 inches) and 7 centimeters (3 inches) respectively. Rotate 
one end of the rod in the flame until it softens. At the same 
time grasp the platinum wire firmly in the forceps about 
1 centimeter (0.5 inch) from the end, and hold it also in the 
o*- <— . ■■■■> 

- VII 1 / 

Fig. XIII. — Test wires — platinum (upper), nichrome (lower) 

138 
















flame. When the rod is soft enough, gently push the hot end 
of the wire into the rod. 

(2) Nichrome. Wind a piece of nichrome wire around a 
match stick. The completed test wires are shown in Fig. XIII. 

6. Pouring liquids 
and transferring 
solids. — (a) Liquids 
can be poured from a 
test tube or dish with¬ 
out spilling by mois¬ 
tening a glass rod with 
the liquid, holding the 
wet rod against the 
edge of the vessel, and 
then pouring the liquid 
slowly down the rod 
(Fig. XIV). 

(6) Liquids should be poured from a bottle by holding the 
bottle as shown in Fig. XV. Note that the stopper and 
bottle are held in the same hand. The stopper is first 
removed by holding the palm of the hand upward and grasp¬ 
ing the stopper between the fingers before the bottle is lifted 



Fig. XIV. — Pouring a liquid down a rod 



Fig. XV. — Pouring a liquid from a 
bottle 


Fig. XVI. — Removing the 
stopper from a bottle 


(Fig. XVI). All stoppers should be removed this way when 
possible, and held between the fingers — not laid down on the 
desk. The drop on the lip of the bottle should be touched 
with the stopper before the latter is put back into the bottle. 

139 

















(c) Solids should never be poured directly from a large 
bottle into a test tube or dish. Use a spoon, spatula, or piece 
of smooth paper; or rotate the bottle slowly so that the solid 



Fig. XVII. — Putting a solid into a 
tube — first step 



Fig. XVIII. — Putting a solid 
ihto a tube — second step 


will roll out in small qu antities. If the solid is very fine or dirty 
(e.g. mercuric oxide or charcoal), catch the solid on a narrow 
strip of paper creased lengthwise, and introduce the solid from 
the paper into the test tube as shown in Figs. XVII, XVIII. 

7. Collecting gases. — Gases are usually collected over 
water in a pneumatic trough ; one form is shown in outline in 

Fig. XIX (right). The bottle 
(or tube) to be filled with gas 
is first filled with water, covered 
with a piece of filter paper, in¬ 
verted (Fig. XIX — left), and 
placed mouth downward on the 
support of the trough, which is 
previously filled with water just 
above the support (Fig. XIX — 
right). The paper is then re¬ 
moved. Glass plates instead of 
filter paper may be used to cover the bottle, but of course 
such covers must be held on when the bottle is inverted and 
placed on the support. 



Fig. XIX. — Pneumatic trough 
in outline (right) ; bottle of 
water covered and inverted 
(left) 


140 











The gas escapes from the delivery tube, bubbles up through 
the water into the vessel, and forces the water out of the 
vessel. Gases not very soluble in water ( e.g. oxygen and 
hydrogen) are collected in this way. 

Some soluble gases, e.g. hydrochloric acid, chlorine, and 
sulfur dioxide, are collected by allowing the gas to flow 
downward into an empty bottle, i.e. by downward displace¬ 
ment, while ammonia and other light gases are collected by 
allowing the gas to flow up¬ 
ward into a bottle, i.e. by 
upward displacement. 

8. Weighing. — Weighing 
may be approximate or accu¬ 
rate. Approximate weighings 
are made on the scales (Fig. 

XX); accurate weighings are 
made on the horn pan balance 
(Fig. XXI) or on the chemical 
balance (Fig. XXII). The 
metric system of weights is 
used in chemistry and should 
be studied before weighing is 
attempted. (See § 10 below.) 

Note these general direc¬ 
tions about weighing: — 

(1) Before weighing, see 
that the scales and balances 
are clean and properly ad¬ 
justed. If out of order, do 
not adjust them yourself, but 
report to the Teacher. 

(2) Put objects on the left 
side and weights on the right. 

Large (or heavy) objects and weights should be put near the 
center of the pan. 

(3) Substances should not be placed directly on the plat¬ 
form or pan, except pieces of certain metals, e.g. zinc or 
aluminum, or porcelain and glass objects. 

In weighing on the scales, put a piece of paper of about 
141 



Fig. XXI. — Horn pan balance 
hanging in a box (open in front 
and closed in back) to protect 
balance from air currents 























equal size on each platform; the paper on the left should be 
creased. Take the substance from the bottle with a clean 
spoon or spatula, or pour it out by rotating the bottle as 
described in § 6 (c) above; if too much is taken out, do not 
put it back into the bottle, but throw it into the waste jar 
or a special bottle. Approximate weighings are made on 
the scales, e.g. the quantities of chemicals usually needed in 
ordinary exercises. Very often, small quantities need not be 

weighed because the quan¬ 
tity can be estimated by 
the eye. Objects and 
quantities weighing over 
100 gm. should be weighed 
on the scales (follow direc¬ 
tions) . 

In weighing on the horn 
pan or the chemical bal¬ 
ance, if the substance itself 
should not be placed di- 
Fig. xxii. — Chemical balance in a rectly on the pan, weigh a 
glass case (front partly raised) gmall watc h crystal Or cru¬ 

cible and then weigh the substance in this vessel. Some¬ 
times a piece of apparatus is hung from the balance hook. 
Accurate weighings are made on the balance, e.g. the exact 
quantities needed in quantitative exercises. Enter the total 
weight at once in the proper place in the Record in the 
laboratory notebook — not on a scrap of paper. Enter the 
weight as grams and a decimal fraction, e.g. 5.29 grams, not 
5 grams, 2 decigrams, and 9 centigrams. Enter all weigh¬ 
ings — temporary and final — in the notebook. 

The process of weighing is as follows : — 

A. Scales. — Put the object, or the paper containing the 
proper substance, on the left side; on the right side put one 
or more weights which are judged to be the approximate 
weight. Now add or remove (substance or) weights until 
the pointer swings the same number of spaces each side of 
the middle division. Weighings of small quantities, e.g. 
5 grams or less, are usually made by sliding a rider along a 
graduated beam on the front of the scale^. 

142 





































B. Chemical balance. — Release the beam by turning the 
screw or lever. The pointer should swing the same (or very 
nearly the same) number of spaces each side of the central 
line. If it does not, consult the Teacher. If it does, proceed 
with the weighing. Put the object ( e.g . crucible, dish, tube, 
or special substance) on the left pan and the weight judged to 
be equal on the right pan. Release the beam carefully by 
turning the screw or lever, and note the movement of the 
pointer. If the added weight is correct, the pointer will 
swing the same (or very nearly the same) number of spaces 
each side of the central line on the scale. If incorrect (as it 
usually is), slowly turn back the screw or lever and bring the 
balance to rest. Add or remove the weight which is next 
heavier or lighter — as needed — and release again. If not 
correct, bring the balance to rest, and change the weights 
accordingly, taking care to add or remove the weights in 
order (i.e. next heavier or lighter). Continue to change the 
weights, bringing the balance to rest each time, until the 
correct weight is obtained, i.e. when the pointer swings the 
same number of spaces each side of the central line as it did at 
the beginning. As soon as the substance or object is weighed, 
note the weights on the pan and record their sum at once in 
the notebook, then compare the weights with those missing 
from the box; if correct, so indicate in the notebook, and 
finally check the total weight by adding the weights as they 
are returned to the box. 

The following rules should be rigidly observed in weighing 
on the balance: — 

(а) Always bring the balance to rest before changing the 
weights, the object, or the substance. 

(б) If on releasing, the beam does not swing, arrest and 
release again, or fan one pan very gently. 

(c) Lift all weights with clean forceps — not with the fin¬ 
gers (Fig. XXIII). 

C. Horn pan balance. — The horn pan balance must be 
counterpoised before each weighing. This is readily done. 
Clean the pans with soft paper or cheesecloth. Allow them to 
swing freely and note which side is lighter by estimating the 
distances the pointer swings to right and left. Add bits of 

143 


wire or compact wads of paper to the proper pan until 
the balance is counterpoised, i.e. until the pointer swings 
equal distances to the right and left. Sometimes the balance 
can be more or less permanently counterpoised by pasting 



Fig. XXIII. — Weights for chemical balance (left) and scales (middle). 
Correct way of lifting weights (right) 


small pieces of paper on the under side of one pan. Proceed 
with the weighing as in B (noting that there is no releasing 
screw). 

9. Measuring. — Liquids are measured accurately in 
graduated cylinders and burettes (frontispiece DD). The 
lowest point of the curved surface of the liquid, called the 
meniscus, is its correct height. 

Time can be saved by learning and remembering that the 
average ordinary test tube (15 X 1.8 centimeters or 6 X 
■f inch) holds about 30 cc. (cubic centimeters), while the large 
test tube (20 X 2.5 centimeters or 8 X 1 inch) holds about 
75 cc. (cubic centimeters). 

10. The metric system. — This system of weights and 
measures is used almost exclusively in chemistry, and should 
be learned, or reviewed, at once. 

The fundamental unit of this system is the meter. It is 
the unit of length and is 39.37 inches long. The meter and 
the other units have multiples and submultiples, which are 
designated by prefixes attached to the particular unit. 
Thus, kilo- is equivalent to 1000, and deci-, centi-, and 
milli- to 0.1, 0.01, and 0.001. Thus : — 

10 millimeters (mm.) = 1 centimeter (cm.) 

10 centimeters = 1 decimeter (dm.) 

10 decimeters = 1 meter (m.) 

In chemistry, the measures of length usually used are the 
millimeter (mm.) and centimeter (cm.); occasionally the 

144 













meter (m.) is used. For example, the normal height of the 
barometer is 760 mm. or 76 cm., the length of tubing used in 
experiments is given in centimeters, and of long pieces of 
apparatus in meters (and a decimal fraction). A com¬ 
parative scale is given in Fig. XXIV. Note that 2.5 cm. = 
1 in. (very nearly). 



Fig. XXIV. — Comparative scale — metric below, English above. On 
the metric scale the numbered divisions are centimeters and the smallest 
are millimeters 


The unit of weight is the gram. It is the one-thousandth 
part of a standard weight called the kilogram. Thus : — 

10 milligrams (mg., mgm.) = 1 centigram (eg.) 

10 centigrams (eg.) = 1 decigram (dg.) 

10 decigrams (dg.) = 1 gram (gm.) 

1000 grams (gm.) = 1 kilogram (kg.) 

A kilogram weighs about 2.2 pounds (avoir.). Large 
weights are often expressed in kilograms (and a decimal 
fraction). A gram weighs 15.43 grains. Small weights are 
expressed in grams. Thus, the weight of an object weighing 
2 grams, 2 centigrams, and 5 milligrams is written, 2.025 
grams (or gm.). 

The unit of volume is the liter. It is equal to the capacity 
of the vessel containing a kilogram of water. A liter equals 
about one quart. The table is : — 

1000 cubic millimeters = 1 cubic centimeter (cc.) 

1000 cubic centimeters = 1 cubic decimeter (cu. dm.) 

1 cubic decimeter = 1 liter (1.) 

In chemistry the cubic centimeter and the liter are the de¬ 
nominations used to measure and express volume. Thus, a 
test tube measuring 15 X 1.8 cm. holds about 30 cc., a large 
tube (20 X 2.5 cm.) holds about 75 cc., and the large test 
greenish glass acid bottles hold 2.5 1. 

145 




An approximate relation (true only in the case of water and 
liquids of the same specific gravity) is 11. = 1 kg. = 1 cu. 
dm. = 1000 cc. = 1000 gm. = 2.2 lb. 

11. Smelling and tasting. — Unfamiliar substances should 
never be smelled or tasted except according to directions, and 
even then with the utmost caution. Never inhale a gas 
vigorously, but waft it gently with the hand toward the nose. 
Never ask another pupil to inhale a gas. Taste acids, bases, 
and salts by touching a minute portion of the dilute solution 
to the tip of the tongue, and as soon as the sensation is 
detected, reject the solution at once — never swallow it. 

12. Accidents. — Cuts, even if slight, should be washed in 
clean, cold water, sterilized with dilute iodine solution, and 
then covered with collodion if slight, or bandaged if severe. 

Burns should be covered with a paste made by mixing 
sodium bicarbonate (baking soda) and carron oil (an emulsion 
of limewater and oil) and then bandaged. 

Acids and alkalies if spilled on the hands or spattered on 
the face should be washed off at once with water; if a burn is 
produced, this may be treated as described above. 

Fires may be extinguished by sand or by a pyrene extin¬ 
guisher. If the clothing catches fire, a damp towel or asbestos 
blanket should be used at once. 

A portable emergency box, or cabinet, containing “ first 
aid ” articles should be kept in a convenient place. For 
contents, see Appendix, § 13, List F. 

13. Laboratory equipment. — These lists include the 
apparatus, chemicals, and supplies needed for the exercises 
in this book. No allowance is made for breakage, duplicate 
corks and rubber stoppers, and extra glass and rubber tubing. 


List A — Individual Outfit. This list includes the 
articles needed by each pupil for the regular exercises. 


1 Blowpipe. 

1 Blowpipe tube. 

5 Bottles, wide mouth, 250 cc. 
1 Bottle, generator, 250 cc. 

1 Bunsen burner. 

1 Cork to fit small test tube. 

1 Cork to fit large test tube. 


1 Crucible and cover, porcelain, 
No. 0. 

1 Crucible block, wood, 10 X 10 
X 2.5 cm. with 3 cm. hole in 
center. 

1 Deflagrating spoon. 

1 Evaporating dish, 7 cm. 


100 Filter papers, 10 cm. 

1 Flask, Erlenmeyer, 250 cc. 

1 Forceps, iron. 

1 Funnel, 65 mm. 

4 Glass plates, 10 X 10 cm. 

1 Glass rod, 15 cm. 

1 Glass tube, 150 cm. 1 
1 Graduated cylinder, 25 cc. 

1 Iron stand, clamp (medium), 
ring (8 cm.). 

1 Matches (box). 

1 Mortar and pestle, 8 cm. 

1 Pinch-clamp, Mohr’s. 2 
1 Pneumatic trough, complete. 3 

1 Rubber stopper, 23 mm., 

1- hole. 4 

2 Rubber stoppers, 23 mm., 

2- hole. 4 

1 Rubber tube, 6 mm. (i in.) 
diam., 60 cm. long (for 
burner). 


1 Rubber tube, fV in. diam., 15 
cm. long (for connectors). 

1 Rubber tube, pressure ( T 3 e in. 
diam.), 15 cm. long (for drop¬ 
ping funnel— Exer. 7). 2 

1 Sponge. 

12 Test tubes, 15 X 1.8 cm. (6 X 
fin.) (“small” test tube). 

3 Test tubes, 20 X 2.5 cm. (8X1 
in.) (“large” test tube). 

1 Test tube brush. 

1 Test tube holder. 

1 Test tube rack. 

1 Test wire —• platinum 7 cm. or 
nichrome 10 cm. (see App., 
§ 5 (d)). 

1 Thistle tube, straight stem. 2 

1 Triangle. 5 

1 Wire gauze, 10 X 10 cm. 

2 Wooden blocks, 15 X 15 X 

2.5 cm. 


List B — Special Apparatus. This list includes the 
special apparatus needed for a class of ten. Numbers in 
parentheses refer to exercises. Refer to the exercises and 
buy only the apparatus needed. 


1 Balance, chemical (4, 18, 22, 

41). 

3 Balances, horn pan (as above). 6 

1 Barometer (20, etc.). 

2 Beakers, 250 cc. (30). 

5 Bottles, 2500 cc. (41). 


2 Burettes, 50 cc. (30). 

1 Burner, gas (50). 

3 Chimneys, lamp (S 25). 

1 Cork borers, set (App., § 5 (c)). 
1 Cylinder, graduated, 1000 cc. 
( 21 ). 


1 To fit the rubber stoppers. 

2 See Exercise 7. The stem of the thistle tube should fit the 
rubber stoppers. 

3 Preferable kind is an indurated fiber Keeler No. 4 provided with a 
shallow flower pot 10 cm. in diameter. An agateware pan may be 
used. 

4 To fit the large test tube. This size (about 23 mm.) also fits the 
average 250 cc. Erlenmeyer flask, the 250 cc. generator bottle, and the 
2500 cc. bottle (acid bottle — See List B). 

5 To fit porcelain crucible. 

6 A chemical balance costing about twenty-five dollars is sufficiently 
accurate. Horn pan balances, if carefully counterpoised, give ac¬ 
ceptable results. (See App., § 8.) 

147 


2 Cylinders, graduated, 500 cc. 1 
2 Cylinders, graduated, 250 cc. 1 

(27, 45). 

2 Cylinders, graduated, 100 cc. 1 
1 File, round (App., § 5 (c)). 

1 File, triangular (App., § 3 (a)). 

1 Hydrometer (heavy) (45). 

3 Jars, 30 X 10 cm. 2 ( 21 ). 

3 Lenses (magnifiers). 3 

2 Magnets (2, etc.). 

5 Pans, iron, 10 cm. 3 

2 Retorts, stoppered, 250 cc. (37). 


1 Scales (App., § 8) (constantly). 

5 Screws, Hofmann (41). 

3 Thermometers, — 10° to 100° C. 3 
5 Tubes, graduated, 100 cc. (21). 

1 Weights for chemical balance, 
2 mg. to 50 gm. 4 

3 Weights for horn pan balance, 
2 mg. to 50 gm. 4 

1 Weights for scales, 5 gm. to 
1000 gm. 3 

3 Wing-top burners (App., § 3 (6)). 


List C — Demonstration Apparatus. This list in¬ 
cludes apparatus — not in other lists — needed for certain 
Supplementary Exercises and for the Teacher’s Exercises. 
Numbers in parentheses refer to exercises. S means Sup¬ 
plementary. 


1 Battery (19, S31, 32, S32, S33). 
1 Battery jar, 12 cm. in diam. 
(32). 

1 Chlorine tube (S 17). 

1 Clamp (large — for condenser) 
(S 11). 


1 Condenser, Liebig, complete 

(S 11). 

2 Electric light bulbs (32). 

1 Hofmann apparatus (19, S32, 
33). 

1 Plug, glass (27). 


List D — Chemicals and Supplies. This list includes 
the quantities of chemicals and supplies needed for the 
exercises in this book. Unless specially marked, the quan¬ 
tities are sufficient for a class of ten. Numbers in paren¬ 
theses refer to exercises. S means Supplementary and T 
means Teacher’s. Starred items may be bought of a local 
dealer. 

Acid, acetic (S 41) . . 250 cc. 

hydrochloric .... 2.51. 

nitric.2.51. 

oxalic (T 8) . . . .25 gm. 

pyrogallic (T 27) . . 50 gm. 

1 Needed in preparing solutions. 

2 A 500 cc. graduated cylinder may be used. 

3 Used frequently. 

4 A chemical balance costing about twenty-five dollars is sufficiently 
accurate. Horn pan balances, if carefully counterpoised, give ac¬ 

ceptable results. (See App., § 8.) 

6 Denatured alcohol is suitable for many experiments. 

148 


salicylic (S 41) ... 5 gm. 

sulfuric.2.5 1. 

Alcohol denatured 5 6 (S 47) 100 cc. 
ethyl 5 (S 41 and List G) 500 cc. 
methyl (See Methanol) 



Alizarin (paste) (S 61) . 10 gm. 

Alum. 250 gm. 

Aluminum acetate (S 61) 25 gm. 
sheet .... 500 sq. cm. 

sulfate. 250 gm. 

wire (41).10 cm. 

Ammonium carbonate (S 51, 

etc.).100 gm. 

chloride. 250 gm. 

dichromate (35) ... 5 gm. 

hydroxide.2.5 1. 

molybdate (56) (See List 

G).25 gm. 

nitrate (S 36) ... 25 gm. 

oxalate.25 gm. 

sulfate.25 gm. 

sulfide.100 cc. 

Antimony chloride (31, 34) 25 gm. 

Asbestos, shredded (41) . 5 gm. 

Baking powder (56)* . . 250 gm. 

Barium carbonate (59) . 25 gm. 

chloride.150 gm. 

chloride (pure) (S 30) . 25 gm. 
nitrate (S 33, S 59) . 25 gm. 

sulfate (59) .... 25 gm. 

Bleaching powder* (23, S 21) 


500 gm. 

Borax*. 250 gm. 

Bromine water (S 46) . 100 cc. 

Cadmium nitrate (38) . 5 gm. 

Calcium (31) .... 5 gm. 

butyrate (S 41) . . . 5 gm. 


carbide (S 40) ... 5 gm. 

carbonate (marble) * . 2.5 kg. 

chloride.100 gm. 

nitrate (S 59) ... 25 gm. 

oxide (lime) * . . . . 500 gm. 


sulfate.100 gm. 

Carbon disulfide . . . 250 cc. 

tetrachloride (S 46, S47) 100 cc. 
Cement* (S 54) . . . 100 gm. 

Chalk.25 gm. 

Charcoal, animal . . . 100 gm. 

blocks (53, S 58) . . 15blk. 

lump.15 lp. 

wood (powd.) . . . 150 gm. 

Cobalt chloride (35) . . 25 gm. 


Cobalt nitrate (35, S 58). 25 gm. 

Cochineal (S 61) . . 

1 gm. 

Copper borings . . . 

. 200 gm. 

bromide (35) . . 

. 25 gm. 

nitrate (35) . . . 

. 25 gm. 

oxide (ic) (powd.) . 

. 100 gm. 

sheet* . 

50 sq. cm. 

sulfate . . . . . 

. 500 gm. 

wire (No. 20)* . . 

. 250 gm. 

wire (No. 30) (22)* 
Dextrose (See Glucose) 

. 250 gm. 

Fehling’s Solution (See 

List G) ... 

. 100 cc. 

Ferric chloride . 

. 50 gm. 

Ferrous sulfate . . . 

. 100 gm. 

sulfide. 

. 150 gm. 

Gasolene* . . . . 

. 250 cc. 

Glass wool (41) . . . 

. 5 gm. 

Glucose . 

. 25 gm. 

Glycerin (T 32) . . . 

. 25 cc. 

Gold leaf (S 20, S 23) 
Hydrogen peroxide* . 

. 1 bk. 

. 250 cc. 

Hydroquinone (S 60) 

(See 

List G) . . . 

. 5 gm. 

Iodine. 

. 25 gm. 

Iron filings .... 

. 100 gm. 

powder. 

. 150 gm. 

thread (steel wool) . 

. 50 gm. 

Joss sticks* . . . 

. 5 pkg. 

Lead dioxide . . . 

. 50 gm. 

monoxide (litharge)* 

. 100 gm. 

nitrate. 

. 100 gm. 

tea (Til)* . . . 

250 sq. cm. 

Litmus cubes (S 32) . 

. 5 gm. 

paper (each color) . 

6 sheets 

Magnesium chloride . 

. 25 gm. 

ribbon. 


sulfate. 


Manganese dioxide (gran.) 

500 gm. 

dioxide (powd.) (41, 

S 44, S 47) 
100 gm. 

sulfate. 

. 25 gm. 

Mercury (S 24) . . . 

. 25 gm. 

chloride (ic) . . . 

. 25 gm. 

nitrate (ous) . . . 

. 25 gm. 

oxide (SI) ... 

. 25 gm. 


149 



























Methanol (S 41) ... 25 cc. 

Molisch’s solution (See 
List G) 

Naphthol (Alpha) (See List 

G).10 gm. 

Nickel chloride (T 35) . 25 gm. 

sulfate (T 35) ... 25 gm. 

Phenol-phthalein solution 

(T 30, S 42) . . . 150 cc. 

Phosphorus (S 5) . . . 5 gm. 

Photograph developer (S 60) (See 
List G) 

Plaster of Paris (S 55) . 125 gm. 

Potassium bromide (S 44, 


S 45, S 46) ... 100 gm. 

bromide (pure) (S 30) . 5 gm. 

carbonate (59) ... 25 gm. 

chlorate (cryst.) . . .100 gm. 

chlorate (powd.) . . 100 gm. 

chlorate (pure) (S 30) . 5 gm. 

chloride.25 gm. 

chromate.10 gm. 

dichromate .... 50 gm. 

ferricyanide .... 25 gm. 
ferrocyanide .... 50 gm. 

hydroxide.100 gm. 


iodide (S 47, S 48, S 50) 75 gm. 
nitrate (powd.) . . .150 gm. 

nitrate (pure) (S 30) . 25 gm. 
permanganate (23) . . 200 gm. 

sulfate (59) .... 25 gm. 

sulfate (pure) (S 50) . 25 gm. 

thiocyanate .... 25 gm. 

Sand*. 500 gm. 

Silver nitrate .... 50 gm. 
sulfate (S 33) ... 10 gm. 


Soda lime (S 35) ... 50 gm. 

Sodium (S 11, S 52) . . 10 gm. 

bicarbonate* (S 7) . . 250 gm. 

carbonate* .... 500 gm. 

chloride.2 kg. 

chloride (pure) (S 30) . 25 gm. 
citrate (See Fehllng’s So¬ 
lution, List G) . . 50 gm. 

dichromate (35) . . 25 gm. 

hydroxide. 500 gm. 

nitrate. 250 gm. 

nitrite (S 27) .... 25 gm. 

peroxide.25 gm. 

phosphate (disodium) . 25 gm. 

sulfate.150 gm. 

sulfate (acid) .... 10 gm. 

sulfite (T 44) (See also de¬ 
veloper List G) . .150 gm. 

thiosulfate (“ hypo ”) 

(S 16, S 60) ... 250 gm. 


Stannous chloride (See 


List G) .... 25 gm. 

Starch*.100 gm. 

Strontium nitrate (pure) 

(S 30). 25 gm. 

Sugar (cane)* .... 250 gm. 

Sulfur (powd.) .... 200 gm. 
roll. 500 gm. 

Tartar emetic (S 38) . . 5 gm. 

Turpentine*.50 cc. 

Zinc chloride (S 14) . . 25 gm. 

dust (4).50 gm. 

granulated .... 1 kg. 

sheet*.100 gm. 

sulfate.100 gm. 


List E — Miscellaneous Supplies. The quantities are 
usually small. Many substances are used only once. 
Numbers in parentheses refer to exercises. S means Sup¬ 
plementary. Bread, candle, candy, carbon (electric light 
— S 31), clay, colored and unbleached cloth, soft coal, 
cotton, feather, gelatin (S 35), hair, horn, iron nails, 
lantern slide plates (S 60), lard (S 42), leather scraps, 
lemon, lye (S 42), maple sugar, phosphorus tipped matches, 
molasses, old mortar (S 53), paper (colored, black, and 

150 






















photographic—S 60), plaster (S 53), potato, quill tooth¬ 
pick, rice, soap, (wax) taper, thread, tooth powder (S 53), 
vaseline, vinegar, whiting ( S 53). 

List F — Emergency Supplies (see App., § 12). 25 gm. 
absorbent cotton, 12 bandages (5 cm.), blanket, 50 gm. boric 
acid solution, 25 gm. camphor solution, 250 gm. carron oil, 
12.5 gm. collodion, 1 book court plaster, fire extinguisher, 
1 pkg. gauze (picric acid), medicine dropper, 1 paper pins, 
sand and scoop, scissors, 1 bottle smelling salts, 250 gm. 
sodium bicarbonate, 1 spool thread, 25 gm. vaseline. 

List G — Solutions. The solutions needed for most 
exercises are approximately 10 per cent (i.e. 10 gm. in 
100 cc. of water). The concentration of special solutions is 
usually given in the directions for these exercises. Certain 
solutions should be made as follows: 

Acetic acid, dilute, 1 vol. to 5 vols. of water. 

Ammonium hydroxide, 1 vol. to 3 vols. of water. 

Ammonium molybdate. Dissolve 15 gm. in 100 cc. of water and pour 
this solution into 100 cc. of nitric acid (1 vol. acid to 1 Vbl. water). 
Ammonium oxalate, 5 per cent. 

Ammonium sulfide, 1 vol. to 1 vol. of water. 

Barium chloride, 5 per cent. Use distilled water or water free from 
sulfates. 

Calcium hydroxide. See Limewater. 

Chlorine water. Saturate water with the gas. 

Cobalt (ous) nitrate, 5 per cent. 

Cochineal. Grind a little cochineal with water, dilute as desired, and 
filter. 

Developer (photographic). Dissolve 2.7 gm. of hydroquinone, 7.6 gm. 
of sodium sulfite, 15 gm. of sodium carbonate, and 0.4 gm. of potas¬ 
sium bromide in 200 cc. of water. 

Fehling’s solution. Dissolve 1.73 gm. of copper sulfate (cryst.) in 15 cc. 
of water. Dissolve 34.6 gm. of sodium citrate and 10 gm. of sodium 
carbonate (anhydrous) in 85 cc. of water. Pour the first solution 
into the second slowly with constant stirring. The final, clear solution 
will keep well and is used as made. (Note this is different from the 
old two-volume solution.) 

Ferric chloride, 5 per cent. 

Ferrous sulfate, 5 per cent. Must be freshly prepared. Keep a few 
pieces of iron in the solution. 

Hydrochloric acid, dilute, 1 vol. to 5 vols. of water. 

Lead salts. Use distilled water or filter. 

151 


Limewater. Slake lime, add considerable water, shake occasionally, 
and siphon off the clear liquid. 

Litmus. As under Cochineal. 

Mercuric chloride, 5 per cent. POISON ! 

Mercurous nitrate, 5 per cent. Add a little mercury. 

Molisch’s solution. Dissolve 5 gm. of alpha-naphthol in 50 cc. of 
ethyl alcohol (95 per cent). 

Nitric acid, dilute, 1 vol. to 5 vols. of water. 

Phenol-phthalein. Dissolve 0.5 gm. in 50 cc. of alcohol and dilute 

slightly with water. . 

Potassium permanganate, 5 per cent. (Add sufficient water to obtain 

the “ very dilute” solution.) 

Potassium thiocyanate, 5 per cent. 

Silver nitrate, 5 per cent. Use distilled water (or water tree trom 
chlorides). 

Silver sulfate, 0.5 per cent. See Silver nitrate. 

Stannous chloride. Reduce concentrated hydrochloric acid with tin, 
dilute with water, and keep tin in this solution. 

Sulfuric acid, dilute, 1 vol. to 5 vols. of water. Pour the acid slowly into 
the water, stirring constantly. 


152 















































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